Color is an important part of human expression.

Color or colour^[1] is the visual perceptual property corresponding in humans to the categories called red, yellow, blue, black, etc. In Psychology, visual perception is the ability to interpret information from Visible light reaching the Eyes The resulting Perception is also Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus Color derives from the spectrum of light (distribution of light energy versus wavelength) interacting in the eye with the spectral sensitivities of the light receptors. A photoreceptor, or photoreceptor cell, is a specialized type of Neuron (nerve cell found in the Eye 's Retina that is capable of Color categories and physical specifications of color are also associated with objects, materials, light sources, etc. , based on their physical properties such as light absorption, reflection, or emission spectra.

Typically, only features of the composition of light that are detectable by humans (wavelength spectrum from 400 nm to 700 nm, roughly) are included, thereby objectively relating the psychological phenomenon of color to its physical specification. Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 Psychology (from Greek grc ψῡχή psȳkhē, "breath life soul" and grc -λογία -logia) is an Academic and Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. Because perception of color stems from the varying sensitivity of different types of cone cells in the retina to different parts of the spectrum, colors may be defined and quantified by the degree to which they stimulate these cells. Cone cells, or cones, are Photoreceptor cells in the Retina of the Eye which function best in relatively bright Light. The vertebrate retina is a light sensitive part inside the inner layer of the Eye. These physical or physiological quantifications of color, however, do not fully explain the psychophysical perception of color appearance. Physiology (from Greek grc φύσις physis, "nature origin" and grc -λογία -logia) is the study of the mechanical physical

The science of color is sometimes called chromatics. It includes the perception of color by the human eye and brain, the origin of color in materials, color theory in art, and the physics of electromagnetic radiation in the visible range (that is, what we commonly refer to simply as Light). Color Theory is the musical alter ego of American singer-keyboardist-songwriter Brian Hazard Art refers to a diverse range of Human activities creations and expressions that are appealing to the Senses or Emotions of a human individual Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700

Colorful reflections upon water

Physics of color

Continuous optical spectrum (designed for monitors with gamma 1. Gamma correction, gamma nonlinearity, gamma encoding, or often simply gamma, is the name of a nonlinear operation used to code and decode luminance 5).

Color, wavelength, frequency and energy of light

Color	/nm	/1014 Hz	/104 cm−1	/eV	/kJ mol−1
Infrared	>1000	<3. Red is any of a number of similar Colors evoked by light consisting predominantly of the longest wavelengths of Light discernible by the human eye in the wavelength The colour orange occurs Yellow is the Color evoked by light that stimulates both the L and M (long and medium wavelength Cone cells of the Retina about equally Green is a Color, the perception of which is evoked by light having a spectrum dominated by energy with a Wavelength of roughly 520–570- nm. Blue is a Colour, the Perception of which is evoked by As the name of a color violet (named after the flower violet) is used in two senses first referring to the color of Light at the short- Wavelength 00	<1. 00	<1. 24	<120
Red	700	4. 28	1. 43	1. 77	171
Orange	620	4. 84	1. 61	2. 00	193
Yellow	580	5. 17	1. 72	2. 14	206
Green	530	5. 66	1. 89	2. 34	226
Blue	470	6. 38	2. 13	2. 64	254
Violet	420	7. 14	2. 38	2. 95	285
Near ultraviolet	300	10. 0	3. 33	4. 15	400
Far ultraviolet	<200	>15. 0	>5. 00	>6. 20	>598

Electromagnetic radiation is characterized by its wavelength (or frequency) and its intensity. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. Frequency is a measure of the number of occurrences of a repeating event per unit Time. When the wavelength is within the visible spectrum (the range of wavelengths humans can perceive, approximately from 380 nm to 740 nm), it is known as "visible light". A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a

Most light sources emit light at many different wavelengths; a source's spectrum is a distribution giving its intensity at each wavelength. Although the spectrum of light arriving at the eye from a given direction determines the color sensation in that direction, there are many more possible spectral combinations than color sensations. In Psychology, sensation is the first stage in the biochemical and neurologic events that begins with the impinging of a stimulus upon the receptor cells of a In fact, one may formally define a color as a class of spectra that give rise to the same color sensation, although such classes would vary widely among different species, and to a lesser extent among individuals within the same species. In each such class the members are called metamers of the color in question. This article is about metamerism as it relates to Colorimetry.

Spectral colors

The familiar colors of the rainbow in the spectrum – named using the Latin word for appearance or apparition by Isaac Newton in 1671 – include all those colors that can be produced by visible light of a single wavelength only, the pure spectral or monochromatic colors. A rainbow is an optical and meteorological phenomenon that causes a spectrum of Light to appear in the Sky when the Sun Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. Sir Isaac Newton, FRS (ˈnjuːtən 4 January 1643 31 March 1727) Biography Early years See also Isaac Newton's early life and achievements The table at right shows approximate frequencies (in terahertz) and wavelengths (in nanometers) for various pure spectral colors. The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a The wavelengths are measured in vacuum (see refraction). This vacuum means "absence of matter" or "an empty area or space" for the cleaning appliance see Vacuum cleaner. Refraction is the change in direction of a Wave due to a change in its Speed.

The color table should not be interpreted as a definitive list – the pure spectral colors form a continuous spectrum, and how it is divided into distinct colors is a matter of culture, taste, and language. A spectrum (plural spectra or spectrums) is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. A language is a dynamic set of visual auditory or tactile Symbols of Communication and the elements used to manipulate them A common list identifies six main bands: red, orange, yellow, green, blue, and violet. Newton's conception included a seventh color, indigo, between blue and violet – but most people do not distinguish it, and most color scientists do not recognize it as a separate color; it is sometimes designated as wavelengths of 420–440 nm. Indigo is the Color on the Electromagnetic spectrum between about 420 and 450 nm in Wavelength, placing it between Blue and violet

The intensity of a spectral color may alter its perception considerably; for example, a low-intensity orange-yellow is brown, and a low-intensity yellow-green is olive-green. Black, when used as a general term is a color that is a Very dark Black, black, or Black, of low Luminance relative to

As discussed in the section on color vision, a light source need not actually be of one single wavelength to be perceived as a pure spectral color. Color vision is the capacity of an organism or machine to distinguish objects based on the Wavelengths (or frequencies) of the Light they reflect or emit

For discussion of non-spectral colors, see below.

Color of objects

The upper disk and the lower disk have exactly the same objective color, and are in identical gray surrounds; based on context differences, humans perceive the squares as having different reflectances, and may interpret the colors as different color categories; see same color illusion. The same color illusion — also known as Adelson's checker shadow illusion, checker shadow illusion and checker shadow — is an Optical illusion

The color of an object depends on both the physics of the object in its environment and the characteristics of the perceiving eye and brain. Physically, objects can be said to have the color of the light leaving their surfaces, which normally depends on the spectrum of that light and of the incident illumination, as well as potentially on the angles of illumination and viewing. Some objects not only reflect light, but also transmit light or emit light themselves (see below), which contribute to the color also. And a viewer's perception of the object's color depends not only on the spectrum of the light leaving its surface, but also on a host of contextual cues, so that the color tends to be perceived as relatively constant: that is, relatively independent of the lighting spectrum, viewing angle, etc. This effect is known as color constancy. Color constancy is an example of Subjective constancy and a feature of the human Color perception system which ensures that the perceived color of objects remains

Some generalizations of the physics can be drawn, neglecting perceptual effects for now:

• Light arriving at an opaque surface is either reflected "specularly" (that is, in the manner of a mirror), scattered (that is, reflected with diffuse scattering), or absorbed – or some combination of these. Reflection is the change in direction of a Wave front at an interface between two different media so that the wave front returns into the medium from which Scattering is a general physical process whereby some forms of Radiation, such as Light, Sound or moving particles for example are forced to deviate from In Physics, absorption of electromagnetic radiation is the process by which the Energy of a Photon is taken up by matter typically the electrons of an

• Opaque objects that do not reflect specularly (which tend to have rough surfaces) have their color determined by which wavelengths of light they scatter more and which they scatter less (with the light that is not scattered being absorbed). If objects scatter all wavelengths, they appear white. If they absorb all wavelengths, they appear black.

• Opaque objects that specularly reflect light of different wavelengths with different efficiencies look like mirrors tinted with colors determined by those differences. An object that reflects some fraction of impinging light and absorbs the rest may look black but also be faintly reflective; examples are black objects coated with layers of enamel or lacquer.

• Objects that transmit light are either translucent (scattering the transmitted light) or transparent (not scattering the transmitted light). If they also absorb (or reflect) light of varying wavelengths differentially, they appear tinted with a color determined by the nature of that absorption (or that reflectance).

• Objects may emit light that they generate themselves, rather than merely reflecting or transmitting light. They may do so because of their elevated temperature (they are then said to be incandescent), as a result of certain chemical reactions (a phenomenon called chemoluminescence), or for other reasons (see the articles Phosphorescence and List of light sources). Incandescence is the emission of Light (visible Electromagnetic radiation) from a hot body due to its temperature Chemiluminescence (sometimes " chemoluminescence " is the emission of Light ( Luminescence) with limited emission of heat as the result of a chemical Phosphorescence is a specific type of Photoluminescence related to fluorescence. This is a list of sources of Light, including both natural and artificial sources and both processes and devices.

• Objects may absorb light and then as a consequence emit light that has different properties. They are then called fluorescent (if light is emitted only while light is absorbed) or phosphorescent (if light is emitted even after light ceases to be absorbed; this term is also sometimes loosely applied to light emitted due to chemical reactions). Fluorescence is a Luminescence that is mostly found as an

For further treatment of the color of objects, see structural color, below.

To summarize, the color of an object is a complex result of its surface properties, its transmission properties, and its emission properties, all of which factors contribute to the mix of wavelengths in the light leaving the surface of the object. The perceived color is then further conditioned by the nature of the ambient illumination, and by the color properties of other objects nearby, via the effect known as color constancy and via other characteristics of the perceiving eye and brain. Color constancy is an example of Subjective constancy and a feature of the human Color perception system which ensures that the perceived color of objects remains

Color perception

Normalized typical human cone cell responses (S, M, and L types) to monochromatic spectral stimuli

Development of theories of color vision

Main article: Color theory

Although Aristotle and other ancient scientists had already written on the nature of light and color vision, it was not until Newton that light was identified as the source of the color sensation. Cone cells, or cones, are Photoreceptor cells in the Retina of the Eye which function best in relatively bright Light. Color Theory is the musical alter ego of American singer-keyboardist-songwriter Brian Hazard Aristotle (Greek Aristotélēs) (384 BC – 322 BC was a Greek philosopher a student of Plato and teacher of Alexander the Great. Color vision is the capacity of an organism or machine to distinguish objects based on the Wavelengths (or frequencies) of the Light they reflect or emit Sir Isaac Newton, FRS (ˈnjuːtən 4 January 1643 31 March 1727) Biography Early years See also Isaac Newton's early life and achievements In 1810, Goethe published his comprehensive Theory of Colors. ˈjoːhan ˈvɔlfgaŋ fɔn ˈgøːtə (in English generally ˈgɝːtə 28 August 1749 22 March 1832 was a German writer Theory of Colours (original German title Zur Farbenlehre) is a book by Johann Wolfgang von Goethe published in 1810 In 1801 Thomas Young proposed his trichromatic theory, based on the observation that any color could be matched with a combination of three lights. Thomas Young (13 June 1773 &ndash 10 May 1829 was an English Polymath who contributed to the scientific understanding of vision, Light Trichromacy is the condition of possessing three independent channels for conveying Color information derived from the three different cone types This theory was later refined by James Clerk Maxwell and Hermann von Helmholtz. James Clerk Maxwell (13 June 1831 &ndash 5 November 1879 was a Scottish mathematician and theoretical physicist. As Helmholtz puts it, "the principles of Newton's law of mixture were experimentally confirmed by Maxwell in 1856. Young's theory of color sensations, like so much else that this marvellous investigator achieved in advance of his time, remained unnoticed until Maxwell directed attention to it. "^[3]

At the same time as Helmholtz, Ewald Hering developed the opponent process theory of color, noting that color blindness and afterimages typically come in opponent pairs (red-green, blue-yellow, and black-white). Karl Ewald Konstantin Hering ( August 5, 1834 &ndash January 26, 1918) was a German Physiologist who did much research The color opponent process is a Color theory that states that the human Visual system interprets information about Color by processing signals from Color blindness, a Color vision deficiency is the inability to perceive differences between some of the Colors that others can distinguish Ultimately these two theories were synthesized in 1957 by Hurvich and Jameson, who showed that retinal processing corresponds to the trichromatic theory, while processing at the level of the lateral geniculate nucleus corresponds to the opponent theory. The lateral geniculate nucleus ( LGN) of the Thalamus is a part of the Brain, which is the primary processor of visual information received from the ^[4]

In 1931, an international group of experts known as the Commission Internationale d'Eclairage (CIE) developed a mathematical color model, which mapped out the space of observable colors and assigned a set of three numbers to each. Established in 1913 and based in Vienna, Austria, the International Commission on Illumination (usually known as the CIE for its French name Commission

Color in the eye

Main article: Color vision

The ability of the human eye to distinguish colors is based upon the varying sensitivity of different cells in the retina to light of different wavelengths. Color vision is the capacity of an organism or machine to distinguish objects based on the Wavelengths (or frequencies) of the Light they reflect or emit Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain The vertebrate retina is a light sensitive part inside the inner layer of the Eye. The retina contains three types of color receptor cells, or cones. Cone cells, or cones, are Photoreceptor cells in the Retina of the Eye which function best in relatively bright Light. One type, relatively distinct from the other two, is most responsive to light that we perceive as violet, with wavelengths around 420 nm. A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a (Cones of this type are sometimes called short-wavelength cones, S cones, or, misleadingly, blue cones. ) The other two types are closely related genetically and chemically. One of them (sometimes called long-wavelength cones, L cones, or, misleadingly, red cones) is most sensitive to light we perceive as yellowish-green, with wavelengths around 564 nm; the other type (sometimes called middle-wavelength cones, M cones, or, misleadingly, green cones) is most sensitive to light perceived as green, with wavelengths around 534 nm.

Light, no matter how complex its composition of wavelengths, is reduced to three color components by the eye. For each location in the visual field, the three types of cones yield three signals based on the extent to which each is stimulated. These values are sometimes called tristimulus values.

The response curve as a function of wavelength for each type of cone is illustrated above. Because the curves overlap, some tristimulus values do not occur for any incoming light combination. For example, it is not possible to stimulate only the mid-wavelength/"green" cones; the other cones will inevitably be stimulated to some degree at the same time. The set of all possible tristimulus values determines the human color space. It has been estimated that humans can distinguish roughly 10 million different colors. ^[5]

The other type of light-sensitive cell in the eye, the rod, has a different response curve. Rod cells, or rods, are Photoreceptor cells in the Retina of the Eye that can function in less intense Light than can the other type In normal situations, when light is bright enough to strongly stimulate the cones, rods play virtually no role in vision at all. ^[6] On the other hand, in dim light, the cones are understimulated leaving only the signal from the rods, resulting in a colorless response. (Furthermore, the rods are barely sensitive to light in the "red" range. ) In certain conditions of intermediate illumination, the rod response and a weak cone response can together result in color discriminations not accounted for by cone responses alone.

Color in the brain

Main article: Color vision

The visual dorsal stream (green) and ventral stream (purple) are shown. Color vision is the capacity of an organism or machine to distinguish objects based on the Wavelengths (or frequencies) of the Light they reflect or emit The dorsal stream is a pathway for visual information that flows through the Visual cortex, the part of the Brain which provides visual processing The primate visual system consists of numerous diverse areas of the Cerebral cortex called the Visual cortex. The ventral stream is responsible for color perception.

While the mechanisms of color vision at the level of the retina are well-described in terms of tristimulus values (see above), color processing after that point is organized differently. A dominant theory of color vision proposes that color information is transmitted out of the eye by three opponent processes, or opponent channels, each constructed from the raw output of the cones: a red-green channel, a blue-yellow channel and a black-white "luminance" channel. Opponent-process theory is a universal psychological and neurological model proposed by Leo Hurvich and Dorothea Jameson 1957 and expanded by his co-worker at This theory has been supported by neurobiology, and accounts for the structure of our subjective color experience. Specifically, it explains why we cannot perceive a "reddish green" or "yellowish blue," and it predicts the color wheel: it is the collection of colors for which at least one of the two color channels measures a value at one of its extremes. A color wheel or color circle is an organization of Color Hues around a circle showing relationships between colors considered to be Primary

The exact nature of color perception beyond the processing already described, and indeed the status of color as a feature of the perceived world or rather as a feature of our perception of the world, is a matter of complex and continuing philosophical dispute (see qualia). " Qualia " (ˈkwɑːliə is "an unfamiliar term for something that could not be more familiar to each of us the ways things seem to us"

Nonstandard color perception

Color deficiency

Main article: Color blindness

If one or more types of a person's color-sensing cones are missing or less responsive than normal to incoming light, that person can distinguish fewer colors and is said to be color deficient or color blind (though this latter term can be misleading; almost all color deficient individuals can distinguish at least some colors). Color blindness, a Color vision deficiency is the inability to perceive differences between some of the Colors that others can distinguish Color blindness, a Color vision deficiency is the inability to perceive differences between some of the Colors that others can distinguish Some kinds of color deficiency are caused by anomalies in the number or nature of cones in the retina. Others (like central or cortical achromatopsia) are caused by neural anomalies in those parts of the brain where visual processing takes place. Achromatopsia ( ACHM) spelled with an s is a medical syndrome that exhibits symptoms relating to at least five separate individual diseases

Tetrachromacy

Main article: Tetrachromacy

While most humans are trichromatic (having three types of color receptors), many animals, known as tetrachromats, have four types. Tetrachromacy is the condition of possessing four independent channels for conveying Color information or possessing four different cones. Tetrachromacy is the condition of possessing four independent channels for conveying Color information or possessing four different cones. These include some species of spiders, most marsupials, birds, reptiles, and many species of fish. Spiders are Predatory Invertebrate Animals that have two body segments, eight legs no chewing mouth parts and no wings Marsupials are an Infraclass of Mammals characterized by a distinctive pouch (called the marsupium) in which females carry their young through Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. Reptiles, or members of the class Reptilia are air-breathing Cold-blooded Vertebrates that have skin covered in scales as opposed to hair or feathers Fish are aquatic Vertebrate animals that are typically ectothermic (previously Cold-blooded) covered with scales, and equipped with two Other species are sensitive to only two axes of color or do not perceive color at all; these are called dichromats and monochromats respectively. A distinction is made between retinal tetrachromacy (having four pigments in cone cells in the retina, compared to three in trichromats) and functional tetrachromacy (having the ability to make enhanced color discriminations based on that retinal difference). As many as half of all women, but only a small percentage of men, are retinal tetrachromats. ^[7] The phenomenon arises when an individual receives two slightly different copies of the gene for either the medium- or long-wavelength cones, which are carried on the x-chromosome, accounting for the differences between genders. ^[7] For some of these retinal tetrachromats, color discriminations are enhanced, making them functional tetrachromats. ^[7]

Synesthesia

In certain forms of synesthesia, perceiving letters and numbers (grapheme–color synesthesia) or hearing musical sounds (music–color synesthesia) will lead to the unusual additional experiences of seeing colors. Synesthesia (also spelled synæsthesia or synaesthesia, plural synesthesiae or synaesthesiae)—from the Ancient Greek (syn meaning "with" Grapheme → color synesthesia is a form of Synesthesia in which an individual's perception of numbers and letters are associated with the experience of colors Behavioral and functional neuroimaging experiments have demonstrated that these color experiences lead to changes in behavioral tasks and lead to increased activation of brain regions involved in color perception, thus demonstrating their reality, and similarity to real color percepts, albeit evoked through a non-standard route. Functional neuroimaging is the use of Neuroimaging technology to measure an aspect of brain function often with a view to understanding the relationship between activity in

Afterimages

After exposure to strong light in their sensitivity range, photoreceptors of a given type become desensitized. For a few seconds after the light ceases, they will continue to signal less strongly than they otherwise would. Colors observed during that period will appear to lack the color component detected by the desensitized photoreceptors. This effect is responsible for the phenomenon of afterimages, in which the eye may continue to see a bright figure after looking away from it, but in a complementary color. Complementary colors are pairs of Colors that are of “opposite” Hue in some Color model.

Afterimage effects have also been utilized by artists, including Vincent van Gogh.

Color constancy

Main article: Color constancy

There is an interesting phenomenon which occurs when an artist uses a limited color palette: the eye tends to compensate by seeing any grey or neutral color as the color which is missing from the color wheel. Color constancy is an example of Subjective constancy and a feature of the human Color perception system which ensures that the perceived color of objects remains In Computer graphics, a palette is either a given finite set of Colors for the management of Digital images (that is a color palette) or Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain E. g. , in a limited palette consisting of red, yellow, black and white, a mixture of yellow and black will appear as a variety of green, a mixture of red and black will appear as a variety of purple, and pure grey will appear bluish.

The trichromatric theory discussed above is strictly true only if the whole scene seen by the eye is of one and the same color, which of course is unrealistic. In reality, the brain compares the various colors in a scene, in order to eliminate the effects of the illumination. If a scene is illuminated with one light, and then with another, as long as the difference between the light sources stays within a reasonable range, the colors of the scene will nevertheless appear constant to us. This was studied by Edwin Land in the 1970s and led to his retinex theory of color constancy. Edwin Herbert Land ( May 7 1909  &ndash March 1 1991) was an American Scientist and inventor. Color constancy is an example of Subjective constancy and a feature of the human Color perception system which ensures that the perceived color of objects remains

Color naming

Main article: Color naming

Colors vary in several different ways, including hue (red vs. A color name is a Noun or Noun phrase that refers to a specific Color. Hue is one of the main properties of a Color described with names such as " Red " " Yellow " etc orange vs. blue), saturation, brightness, and gloss. In Colorimetry and Color theory, colorfulness, chroma, and saturation are related but distinct concepts referring to the perceived intensity Brightness is an attribute of Visual perception in which a source appears to emit or reflect a given amount of Light. List of optical topics Gloss is an Optical property which is based on the interaction of light with physical characteristics of a surface Some color words are derived from the name of an object of that color, such as "orange" or "salmon", while others are abstract, like "red".

Different cultures have different terms for colors, and may also assign some color names to slightly different parts of the spectrum: for instance, the Chinese character 青 (rendered as qīng in Mandarin and ao in Japanese) has a meaning that covers both blue and green; blue and green are traditionally considered shades of "青. A color name is a Noun or Noun phrase that refers to a specific Color. A Chinese character, also known as a Han character ( is a Logogram used in writing Chinese (hanzi Japanese ( Standard Mandarin, also known as Standard Spoken Chinese, is the official modern Chinese spoken language used in mainland China and Taiwan is a language spoken by over 130 million people in Japan and in Japanese emigrant communities The English language makes a distinction between Blue and Green but some Languages do not "

In the 1969 study Basic Color Terms: Their Universality and Evolution, Brent Berlin and Paul Kay describe a pattern in naming "basic" colors (like "red" but not "red-orange" or "dark red" or "blood red", which are "shades" of red). Basic Color Terms Their Universality and Evolution (1969 (ISBN 1-57586-162-3 is a book by Brent Berlin and Paul Kay. Brent Berlin is an American anthropologist, most famous for his work with linguist Paul Kay on Color, Basic Color Terms This article is about the linguistics professor For the English comedian see Paul Kaye. All languages that have two "basic" color names distinguish dark/cool colors from bright/warm colors. The next colors to be distinguished are usually red and then blue or green. All languages with six "basic" colors include black, white, red, green, blue and yellow. The pattern holds up to a set of twelve: black, grey, white, pink, red, orange, yellow, green, blue, purple, brown, and azure (distinct from blue in Russian and Italian but not English). Azure is a Blue Color on the HSV color wheel at 210 degrees Azure is the Hue that is halfway between Blue and Cyan Russian ( transliteration:,) is the most geographically widespread language of Eurasia, the most widely spoken of the Slavic languages Italian ( or lingua italiana) is a Romance language spoken by about 63 million people as a First language, primarily in Italy.

Associations

Individual colors have a variety of cultural associations such as national colors (in general described in individual color articles and color symbolism). National colours are frequently part of a country's set of National symbols. For the physiological perception of color see Color and Color vision. The field of color psychology attempts to identify the effects of color on human emotion and activity. For the physiological perception of color see Color and Color vision. Chromotherapy is a form of alternative medicine attributed to various Eastern traditions. Chromotherapy, sometimes called color therapy or colorology, is an Alternative medicine method The term alternative medicine, as used in the modern western world encompasses any healing practice "that does not fall within the realm of conventional Medicine.

Health effects

When the color spectrum of artificial lighting is mismatched to that of sunlight, material health effects may arise including increased incidence of headache. Sunlight, in the broad sense is the total spectrum of the Electromagnetic radiation given off by the Sun. A headache ( cephalalgia in medical terminology is a condition of pain in the Head; sometimes Neck or upper back pain may also be interpreted This phenomenon is often coupled with adverse effects of over-illumination, since many of the same interior spaces that have color mismatch also have higher light intensity than desirable for the task being conducted in that space. Over-illumination is the presence of lighting intensity ( Illuminance) beyond that required for a specified activity

Measurement and reproduction of color

Relation to spectral colors

The CIE 1931 color space chromaticity diagram. In the study of the perception of Color, one of the first mathematically defined Color spaces was the CIE 1931 XYZ color space (also known as CIE 1931 color space In the study of the perception of Color, one of the first mathematically defined Color spaces was the CIE 1931 XYZ color space (also known as CIE 1931 color space The outer curved boundary is the spectral (or monochromatic) locus, with wavelengths shown in nanometers. Note that the colors depicted depend on the color space of the device on which you are viewing the image, and therefore may not be a strictly accurate representation of the color at a particular position, and especially not for monochromatic colors. A Color model is an abstract mathematical model describing the way Colors can be represented as Tuples of numbers typically as three or four values or color components

Most light sources are mixtures of various wavelengths of light. However, many such sources can still have a spectral color insofar as the eye cannot distinguish them from monochromatic sources. For example, most computer displays reproduce the spectral color orange as a combination of red and green light; it appears orange because the red and green are mixed in the right proportions to allow the eye's red and green cones to respond the way they do to orange.

A useful concept in understanding the perceived color of a non-monochromatic light source is the dominant wavelength, which identifies the single wavelength of light which produces a sensation most similar to the light source. In color science, the dominant wavelength and complementary wavelength are ways of describing non-spectral (polychromatic light mixtures in terms of the spectral Dominant wavelength is roughly akin to hue. Hue is one of the main properties of a Color described with names such as " Red " " Yellow " etc

Of course, there are many color perceptions that by definition cannot be pure spectral colors due to desaturation or because they are purples (mixtures of red and violet light, from opposite ends of the spectrum). In Colorimetry and Color theory, colorfulness, chroma, and saturation are related but distinct concepts referring to the perceived intensity Some examples of necessarily non-spectral colors are the achromatic colors (black, gray and white) and colors such as pink, tan, and magenta. Pink is a pale Red Color that was first recorded in the 17th century to describe the pale red Flowers of pinks, Flowering plants Magenta is a purplish red Color evoked by lights with less power in yellowish-green Wavelengths than in blue and red wavelengths ( complements of magenta have

Two different light spectra which have the same effect on the three color receptors in the human eye will be perceived as the same color. This is exemplified by the white light that is emitted by fluorescent lamps, which typically has a spectrum consisting of a few narrow bands, while daylight has a continuous spectrum. The human eye cannot tell the difference between such light spectra just by looking into the light source, although reflected colors from objects can look different. (This is often exploited e. g. to make fruit or tomatoes look more brightly red in shops. The term fruit has different meanings dependent on context and the term is not synonymous in Food preparation and Biology. The tomato ( Solanum lycopersicum, syn Lycopersicon lycopersicum) is a herbaceous usually sprawling plant in the Solanaceae or nightshade family )

Similarly, most human color perceptions can be generated by a mixture of three colors called primaries. This is used to reproduce color scenes in photography, printing, television and other media. There are a number of methods or color spaces for specifying a color in terms of three particular primary colors. A Color model is an abstract mathematical model describing the way Colors can be represented as Tuples of numbers typically as three or four values or color components Each method has its advantages and disadvantages depending on the particular application.

No mixture of colors, though, can produce a fully pure color perceived as completely identical to a spectral color, although one can get very close for the longer wavelengths, where the chromaticity diagram above has a nearly straight edge. In the study of the perception of Color, one of the first mathematically defined Color spaces was the CIE 1931 XYZ color space (also known as CIE 1931 color space For example, mixing green light (530 nm) and blue light (460 nm) produces cyan light that is slightly desaturated, because response of the red color receptor would be greater to the green and blue light in the mixture than it would be to a pure cyan light at 485 nm that has the same intensity as the mixture of blue and green.

Because of this, and because the primaries in color printing systems generally are not pure themselves, the colors reproduced are never perfectly saturated colors, and so spectral colors cannot be matched exactly. However, natural scenes rarely contain fully saturated colors, thus such scenes can usually be approximated well by these systems. The range of colors that can be reproduced with a given color reproduction system is called the gamut. In color reproduction including Computer graphics and Photography, the gamut, or color gamut (pronounced /ˈgæmət/ is a certain complete The CIE chromaticity diagram can be used to describe the gamut. Established in 1913 and based in Vienna, Austria, the International Commission on Illumination (usually known as the CIE for its French name Commission

Another problem with color reproduction systems is connected with the acquisition devices, like cameras or scanners. The characteristics of the color sensors in the devices are often very far from the characteristics of the receptors in the human eye. In effect, acquisition of colors that have some special, often very "jagged," spectra caused for example by unusual lighting of the photographed scene can be relatively poor.

Species that have color receptors different from humans, e. g. birds that may have four receptors, can differentiate some colors that look the same to a human. Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. In such cases, a color reproduction system 'tuned' to a human with normal color vision may give very inaccurate results for the other observers.

The next problem is different color response of different devices. For color information stored and transferred in a digital form, color management technique based on ICC profiles attached to color data and to devices with different color response helps to avoid deformations of the reproduced colors. In digital imaging systems color management is the controlled conversion between the Color representations of various devices such as Image scanners Digital In Color management, an ICC profile is a set of data that characterizes a color input or output device or a Color space, according to standards promulgated by the The technique works only for colors in gamut of the particular devices, e. In color reproduction including Computer graphics and Photography, the gamut, or color gamut (pronounced /ˈgæmət/ is a certain complete g. it can still happen that your monitor is not able to show you real color of your goldfish even if your camera can receive and store the color information properly and vice versa.

Pigments and reflective media

Main article: Pigment

Pigments are chemicals that selectively absorb and reflect different spectra of light. For the drug referred to as "pigment" see Black tar heroin. When a surface is painted with a pigment, light hitting the surface is reflected, minus some wavelengths. This subtraction of wavelengths produces the appearance of different colors. Most paints are a blend of several chemical pigments, intended to produce a reflection of a given color.

Pigment manufacturers assume the source light will be white, or of roughly equal intensity across the spectrum. White is a Color, the perception which is evoked by Light that stimulates all three types of color sensitive Cone cells in the Human eye If the light is not a pure white source (as in the case of nearly all forms of artificial lighting), the resulting spectrum will appear a slightly different color. Red paint, viewed under blue light, may appear black. Red is any of a number of similar Colors evoked by light consisting predominantly of the longest wavelengths of Light discernible by the human eye in the wavelength Blue is a Colour, the Perception of which is evoked by Black is the Color of objects that do not emit or Reflect Light in any part of the Visible spectrum; they absorb all such frequencies of Red paint is red because it reflects only the red components of the spectrum. Blue light, containing none of these, will create no reflection from red paint, creating the appearance of black.

Structural color

Structural colors are colors caused by interference effects rather than by pigments. Color effects are produced when a material is scored with fine parallel lines, formed of a thin layer or of two or more parallel thin layers, or otherwise composed of microstructures on the scale of the color's wavelength. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. If the microstructures are spaced randomly, light of shorter wavelengths will be scattered preferentially to produce Tyndall effect colors: the blue of the sky, the luster of opals, and the blue of human irises. The Tyndall effect is an effect of light Scattering by colloidal particles or particles in suspension. OPAL ( Open Pool Australian Lightwater reactor) is a 20 megawatt pool-type nuclear research reactor that was officially opened in April 2007 If the microstructures are aligned in arrays, for example the array of pits in a CD, they behave as a diffraction grating: the grating reflects different wavelengths in different directions due to interference phenomena, separating mixed "white" light into light of different wavelengths. In Optics, a Diffraction grating is an optical component with a regular pattern which splits ( diffracts) light into several beams travelling in different In physics interference is the addition ( superposition) of two or more Waves that result in a new wave pattern If the structure is one or more thin layers then it will reflect some wavelengths and transmit others, depending on the layers' thickness.

Structural color is responsible for the blues and greens of the feathers of many birds (the blue jay, for example), as well as certain butterfly wings and beetle shells. Variations in the pattern's spacing often give rise to an iridescent effect, as seen in peacock feathers, soap bubbles, films of oil, and mother of pearl, because the reflected color depends upon the viewing angle. The term peafowl refers to Gallinaceous Birds classified within the genera Rheinardia Argusianus Afropavoand Pavo A soap bubble is a very thin film of Soap water that forms a Sphere with an iridescent Surface. Nacre, also known as mother of pearl, is an organic-inorganic Composite material produced by some Mollusks as an inner shell layer Peter Vukusic has carried out research in butterfly wings and beetle shells using electron micrography, and has since helped develop a range of "photonic" cosmetics using structural color. An electron microscope is a type of Microscope that uses Electrons to illuminate a specimen and create an enlarged image Photonics is the science of generating controlling and detecting Photons particularly in the visible and near Infra-red spectrum, but ^[8]

Structural color is studied in the field of thin-film optics. Thin-film optics is the branch of Optics that deals with very thin structured layers of different materials A layman's term that describes particularly the most ordered or the most changeable structural colors is iridescence. Iridescence is an Optical phenomenon in which Hue changes with the angle from which a surface is viewed

Additional terms

• Hue: the color's direction from white, for example in a color wheel or chromaticity diagram. Hue is one of the main properties of a Color described with names such as " Red " " Yellow " etc A color wheel or color circle is an organization of Color Hues around a circle showing relationships between colors considered to be Primary In the study of the perception of Color, one of the first mathematically defined Color spaces was the CIE 1931 XYZ color space (also known as CIE 1931 color space
• Colorfulness, chroma, or saturation: how "intense" or "concentrated" a color is; also known as chroma or purity. In Colorimetry and Color theory, colorfulness, chroma, and saturation are related but distinct concepts referring to the perceived intensity
• Value, brightness, or lightness: how light or dark a color is.
• Tint: a color made lighter by adding white. “Tint” redirects here For other uses see Tint (disambiguation In Color theory, a tint is the mixture of a Color with
• Shade: a color made darker by adding black. “Tint” redirects here For other uses see Tint (disambiguation In Color theory, a tint is the mixture of a Color with

See also

• International Commission on Illumination
• International Color Consortium
• List of colors
• Primary color
• Secondary color
• Tertiary color
• Neutral color

References

External links and sources

• Bibliography Database on Color Theory, Buenos Aires University
• Comparative article examining Goethean and Newtonian Color
• Color entry at the Stanford Encyclopedia of Philosophy by Barry Maund
• Why are things colored?
• Why Should Engineers and Scientists Be Worried About Color?
• Color, Contrast & Dimension in News Design