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Color (
American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American English is the most influential form of ...
) or colour (
Commonwealth English The use of the English language English is a West Germanic languages, West Germanic language first spoken in History of Anglo-Saxon England, early medieval England, which has eventually become the World language, leading language of inte ...
) is the visual perceptual
property Property is a system of rights that gives people legal control of valuable things, and also refers to the valuable things themselves. Depending on the nature of the property, an owner of property may have the right to Consumable, consume, alter, ...
corresponding in
humans Humans (''Homo sapiens'') are the most populous and widespread species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species ...
to the categories called ''blue'', ''green'', ''red'', etc. Color derives from the
spectrum of light
spectrum of light
(distribution of
light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that can be visual perception, perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 ...

light
power versus
wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase (waves), phase on the wave, such as two adjac ...

wavelength
) interacting in the eye with the spectral sensitivities of the
light receptor
light receptor
s. Color categories and physical specifications of color are also associated with objects or materials based on their physical properties such as light absorption, reflection, or emission spectra. By defining a
color space A color space is a specific organization of colors. In combination with color profiling supported by various physical devices, it supports reproducible representations of color -- whether such representation entails an analog signal, analog or a ...
colors can be identified numerically by their coordinates. Because perception of color stems from the varying
spectral sensitivity Spectral sensitivity is the relative efficiency of detection, of light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that can be visual perception, perceived by the human eye. Visible ...
of different types of
cone cells A cone is a three-dimensional space, three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the Apex (geometry), apex or vertex (geometry), vertex. A cone is for ...
in the
retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some Mollusca, molluscs. The optics of the eye create a Focus (optics), focused two-dimensional image of the visual world on ...

retina
to different parts of the spectrum, colors may be defined and quantified by the degree to which they stimulate these cells. These physical or
physiological Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, B ...
quantifications of color, however, do not fully explain the psychophysical perception of color appearance. The science of color is sometimes called ''chromatics'', ''
colorimetry Colorimetry is "the science and technology used to quantify and describe physically the human color perception." It is similar to spectrophotometry, but is distinguished by its interest in reducing spectra to the physical correlates of color perce ...
'', or simply ''color science''. It includes the perception of color by the
human eye The human eye is a organ (anatomy), sense organ that reacts to light and allows Visual perception, vision. Rod cell, Rod and Cone cell, cone cells in the retina are photoreceptive cells which are able to detect Light, visible light and convey thi ...

human eye
and brain, the origin of color in materials,
color theory In the visual arts, color theory is a body of practical guidance to color mixing and the visual effects of a specific color combination. Color terminology based on the color wheel and its geometry separates colors into primary color, secondary ...
in
art Art is a diverse range of (products of) human activities involving creative imagination to express technical proficiency, beauty, emotional power, or conceptual ideas. There is no generally agreed definition of what constitutes art, and i ...
, and the
physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force. "Physical scien ...

physics
of
electromagnetic radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force. ...
in the visible range (that is, what is commonly referred to simply as ''
light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that can be visual perception, perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 ...

light
'').


Physics of color

Electromagnetic radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force. ...
is characterized by its
wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase (waves), phase on the wave, such as two adjac ...

wavelength
(or
frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also referred to as temporal frequency, which emphasizes the contrast to spatial frequency and angular frequency. Frequency is measured in Hertz (unit), hertz ( ...

frequency
) and its intensity. When the wavelength is within the
visible spectrum File:Light Amplification by Stimulated Emission of Radiation.jpg, Laser beams with visible spectrum The visible spectrum is the portion of the electromagnetic spectrum that is visual perception, visible to the human eye. Electromagnetic radiation ...
(the range of wavelengths humans can perceive, approximately from 390  nm to 700 nm), it is known as "visible
light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that can be visual perception, perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 ...

light
". 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
sensationSensation refers to the processing of sense Sense relates to any of the systems and corresponding organs involved in sensation, i.e. the physical process of responding to Stimulus (physiology), stimuli and providing data for perception. During sensa ...
in that direction, there are many more possible spectral combinations than color sensations. 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 effect can be visualized by comparing the light sources'
spectral power distribution In radiometry, photometry (optics), photometry, and color science, a spectral power distribution (SPD) measurement describes the Power (physics), power per unit area per unit wavelength of an illumination (lighting), illumination (radiant exitance ...
s and the resulting colors.


Spectral colors

The familiar colors of the
rainbow A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to ...

rainbow
in the
spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without steps, across a Continuum (theory), continuum. The word was first used scientifically in optics to describe the ...
—named using the
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, it became the ...

Latin
word for ''appearance'' or ''apparition'' by
Isaac Newton Sir Isaac Newton (25 December 1642 – 20 March Old Style and New Style dates, 1726/27) was an English mathematician, physicist, astronomer, theologian, and author (described in his time as a "natural philosophy, natural philosopher") ...

Isaac Newton
in 1671—include all those colors that can be produced by visible
light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that can be visual perception, perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 ...

light
of a single wavelength only, the ''pure spectral'' or ''monochromatic'' colors. The table at right shows approximate frequencies (in tera
hertz The hertz (symbol: Hz) is the unit Unit may refer to: Arts and entertainment * UNIT, a fictional military organization in the science fiction television series ''Doctor Who'' * Unit of action, a discrete piece of action (or beat) in a theatric ...

hertz
) and wavelengths (in
nanometer Image:Chiraltube.png, one nanometric carbon nano tube, photographed with Scanning Tunneling Microscope file:EM Spectrum Properties edit.svg, 330px, Different lengths as in respect to the Electromagnetic spectrum, measured by the Metre and its der ...
s) for various pure spectral colors. The wavelengths listed are as measured in air or
vacuum A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or "Void (astronomy), void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Ph ...

vacuum
(see
refractive index In optics, the refractive index (also known as refraction index or index of refraction) of a optical medium, material is a dimensionless number that describes how fast EM radiation, light travels through the material. It is defined as :n = \frac, ...

refractive index
). 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
linguistically
linguistically
is a matter of culture and historical contingency (although people everywhere have been shown to ''perceive'' colors in the same way). A common list identifies six main bands: red, orange, yellow, green, blue, and violet. Newton's conception included a seventh color,
indigo InterGlobe Aviation Ltd d/b/a IndiGo is an Indian low-cost airline headquartered in Gurgaon, Haryana, India. It is the largest List of airlines of India, airline in India by passengers carried and fleet size, with a 57% domestic market share ...

indigo
, between blue and violet. It is possible that what Newton referred to as blue is nearer to what today is known as
cyan Cyan () is a greenish-blue color. It is evoked by light with a predominant wavelength of between 490 and 520 nm, between the wavelengths of green and blue Blue is one of the three primary color, primary colours of pigments in painting and ...
, and that indigo was simply the dark blue of the
indigo dye Indigo dye is an organic compound with a distinctive indigo, blue color. Historically, indigo was a natural dye extracted from the leaves of some plants of the Indigofera#Uses, ''Indigofera'' genus, in particular ''Indigofera tinctoria''; dye-bear ...
that was being imported at the time. The ''intensity'' of a spectral color, relative to the context in which it is viewed, may alter its perception considerably; for example, a low-intensity orange-yellow is
brown Brown is a composite color Color ( American English), or colour ( Commonwealth English), is the characteristic of visual perception described through color ''categories'', with names such as red, orange (colour), orange, yellow, green, bl ...
, and a low-intensity yellow-green is
olive green Olive is a dark yellowish-green color, like that of unripe or green olive The olive, known by the botanical name ''Olea europaea'', meaning "European olive", is a species In biology, a species is the basic unit of biological classificat ...
.


Color of objects

The color of an object depends on the physics of the object in its environment, the physics of light in its environment, and the characteristics of the perceiving eye and
brain A brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as Visual perception, vision. It ...
. Physically, objects can be said to have the color of the light leaving their surfaces if it travels through the vacuum of space at speed and does not pass through a physical medium such as a
prism An optical prism is a transparent optics, optical element with flat, polished surfaces that refraction, refract light. At least one surface must be angled—elements with two parallel surfaces are not prisms. The traditional geometrical shape o ...

prism
. The perceived color normally depends on the spectrum of the incident illumination, the wave velocity, the reflectance properties of the surface, and potentially on the angles of illumination and viewing. Some objects not only reflect light, but also transmit light or emit light themselves, which also contributes to the color. 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 color differences between objects can be discerned mostly independent of the lighting spectrum, viewing angle, etc. This effect is known as
color constancy are recognized as being the same in sun and shade Image:ColourIllusion2.jpg, upright=1.2, In these two pictures, the second card from the left seems to be a stronger shade of pink in the upper one than in the lower one. In fact they are the ...
. Some generalizations of the physics can be drawn, neglecting perceptual effects for now: *Light arriving at an
opaque Opacity or opaque may refer to: * Impediments to (especially, visible) light: ** Opacities, absorption coefficients ** Opacity (optics), property or degree of blocking the transmission of light * Metaphors derived from literal optics: ** Opaque con ...
surface is either reflected " specularly" (that is, in the manner of a mirror),
scattered
scattered
(that is, reflected with diffuse scattering), or absorbed—or some combination of these. *Opaque objects that do not reflect specularly (which tend to have rough surfaces) have their color determined by which wavelengths of light they scatter strongly (with the light that is not scattered being absorbed). If objects scatter all wavelengths with roughly equal strength, 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 various 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 from having excited electrons, rather than merely reflecting or transmitting light. The electrons may be excited due to elevated temperature (''
incandescence The incandescent metal embers of the spark used to light this blue color comes from the quantized transitions that result from the oxidation of CH radicals. Incandescence is the emission of electromagnetic radiation In physics P ...

incandescence
''), as a result of chemical reactions (''
chemiluminescence Chemiluminescence (also chemoluminescence) is the emission of light ( luminescence) as the result of a chemical reaction. There may also be limited emission of heat. Given reactants A and B, with an excited intermediate ◊, : ''A+ ''B→ '' ...

chemiluminescence
''), after absorbing light of other frequencies ("
fluorescence light. Fluorescence is the emission of light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that can be visual perception, perceived by the human eye. Visible light is usually defi ...

fluorescence
" or "
phosphorescence Phosphorescence is a type of photoluminescence related to fluorescence. When exposed to light (radiation) of a shorter wavelength, a phosphorescent substance will glow, absorbing the light and reemitting it at a longer wavelength. Unlike flu ...

phosphorescence
") or from electrical contacts as in
light-emitting diode A light-emitting diode (LED) is a semiconductor A semiconductor material has an Electrical resistivity and conductivity, electrical conductivity value falling between that of a Electrical conductor, conductor, such as metallic copper, ...
s, or other
light source Light or visible light is electromagnetic radiation In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies ...
s. 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 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, and via other characteristics of the perceiving eye and brain.


Perception


Development of theories of color vision

Although
Aristotle Aristotle (; grc-gre, Ἀριστοτέλης ''Aristotélēs'', ; 384–322 BC) was a Greek philosopher A philosopher is someone who practices philosophy. The term ''philosopher'' comes from the grc, φιλόσοφος, , translit ...

Aristotle
and other ancient scientists had already written on the nature of light and color vision, it was not until
Newton Newton most commonly refers to: * Isaac Newton (1642–1726/1727), English scientist * Newton (unit), SI unit of force named after Isaac Newton Newton may also refer to: Arts and entertainment * Newton (film), ''Newton'' (film), a 2017 Indian fil ...

Newton
that light was identified as the source of the color sensation. In 1810,
Goethe Johann Wolfgang von Goethe (28 August 1749 – 22 March 1832) was a German poet, playwright, novelist, scientist, statesman, theatre director, critic, and amateur artist. His works include: four novels; epic poetry, epic and lyric poetry; prose ...

Goethe
published his comprehensive '' Theory of Colors'' in which he provided a rational description of colour experience, which 'tells us how it originates, not what it is'. (Schopenhauer) In 1801
Thomas Young
Thomas Young
proposed his
trichromatic theory Trichromacy or trichromatism is the possessing of three independent channels for conveying color information, derived from the three different types of cone cells in the eye. Organisms with trichromacy are called trichromats. The normal explan ...
, based on the observation that any color could be matched with a combination of three lights. This theory was later refined by
James Clerk Maxwell James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish scientist A scientist is a person who conducts Scientific method, scientific research to advance knowledge in an Branches of science, area of interest. In classica ...

James Clerk Maxwell
and
Hermann von Helmholtz Hermann Ludwig Ferdinand von Helmholtz (31 August 1821 – 8 September 1894) was a German physicist A physicist is a scientist A scientist is a person who conducts Scientific method, scientific research to advance knowledge in an Branch ...

Hermann von Helmholtz
. 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 marvelous investigator achieved in advance of his time, remained unnoticed until Maxwell directed attention to it." At the same time as Helmholtz,
Ewald Hering Karl Ewald Konstantin Hering (5 August 1834 – 26 January 1918) was a German physiologist Physiology (; ) is the scientific study of Function (biology), functions and mechanism (biology), mechanisms in a life, living system. As a Branches ...

Ewald Hering
developed the
opponent process 360px, Diagram of the opponent process The opponent process is a color theory that states that the human visual system The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing ...
theory of color, noting that
color blindness Color blindness (color vision deficiency) is the decreased ability to see color or differences in color Color ( American English), or colour ( Commonwealth English), is the characteristic of visual perception described through color ...

color blindness
and afterimages typically come in opponent pairs (red-green, blue-orange, yellow-violet, and black-white). 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 The lateral geniculate nucleus (LGN; also called the lateral geniculate body or lateral geniculate complex) is a relay center in the thalamus for the visual pathway. It is a small, ovoid, ventral projection of the thalamus where the thalamus connec ...

lateral geniculate nucleus
corresponds to the opponent theory. In 1931, an international group of experts known as the ''Commission internationale de l'éclairage'' (
CIE CIE may refer to: Organizations * Cambridge International Examinations, an international examination board * Center for International Education at the University of Massachusetts-Amherst * Cleveland Institute of Electronics, a private technical an ...
) developed a mathematical color model, which mapped out the space of observable colors and assigned a set of three numbers to each.


Color in the eye

The ability of the
human eye The human eye is a organ (anatomy), sense organ that reacts to light and allows Visual perception, vision. Rod cell, Rod and Cone cell, cone cells in the retina are photoreceptive cells which are able to detect Light, visible light and convey thi ...

human eye
to distinguish colors is based upon the varying sensitivity of different cells in the
retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some Mollusca, molluscs. The optics of the eye create a Focus (optics), focused two-dimensional image of the visual world on ...

retina
to light of different
wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase (waves), phase on the wave, such as two adjac ...

wavelength
s. Humans are
trichromatic Trichromacy or trichromatism is the possessing of three independent channels for conveying color Color ( American English), or colour ( Commonwealth English), is the characteristic of visual perception described through color ''categor ...
—the retina contains three types of color receptor cells, or
cone A cone is a three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the apex or vertex. A cone is formed by a set of line segments, half-lines, or lines c ...
s. One type, relatively distinct from the other two, is most responsive to light that is perceived as blue or blue-violet, with wavelengths around 450 nm; cones of this type are sometimes called ''short-wavelength cones'' or ''S cones'' (or misleadingly, ''blue cones''). The other two types are closely related genetically and chemically: ''middle-wavelength cones'', ''M cones'', or ''green cones'' are most sensitive to light perceived as green, with wavelengths around 540 nm, while the ''long-wavelength cones'', ''L cones'', or ''red cones'', are most sensitive to light that is perceived as greenish yellow, with wavelengths around 570 nm. Light, no matter how complex its composition of wavelengths, is reduced to three color components by the eye. Each cone type adheres to the
principle of univariance A principle is a proposition or value that is a guide for behavior or evaluation. In law Law is a system A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole ...
, which is that each cone's output is determined by the amount of light that falls on it over all wavelengths. 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 amounts of stimulation are sometimes called ''tristimulus values''. The response curve as a function of wavelength varies for each type of cone. 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 (so-called "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. The other type of light-sensitive cell in the eye, the rod, has a different response curve. In normal situations, when light is bright enough to strongly stimulate the cones, rods play virtually no role in vision at all. 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. These effects, combined, are summarized also in the
Kruithof curve 400px, The Kruithof curve, with an example light source; CIE Standard Illuminant D65, D65 (Northern daylight), inside the pleasing region. The Kruithof curve describes a region of illuminance levels and color temperatures that are often viewed a ...

Kruithof curve
, that describes the change of color perception and pleasingness of light as function of temperature and intensity.


Color in the brain

While the mechanisms of color vision at the level of the
retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some Mollusca, molluscs. The optics of the eye create a Focus (optics), focused two-dimensional image of the visual world on ...

retina
are well-described in terms of tristimulus values, 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 process 360px, Diagram of the opponent process The opponent process is a color theory that states that the human visual system The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing ...
es, 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. This theory has been supported by neurobiology, and accounts for the structure of our subjective color experience. Specifically, it explains why humans cannot perceive a "reddish green" or "yellowish blue", and it predicts the
color wheel A color wheel or color circle is an abstract illustrative organization of color Color ( American English), or colour ( Commonwealth English), is the characteristic of visual perception described through color ''categories'', with names ...
: it is the collection of colors for which at least one of the two color channels measures a value at one of its extremes. 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—a type of
qualia In philosophy and certain models of psychology, qualia ( or ; singular form: quale) are defined as individual instances of Subjectivity, subjective, consciousness, conscious experience. The term ''qualia'' derives from the Latin neuter plural form ...
—is a matter of complex and continuing philosophical dispute.


Nonstandard color perception


Color deficiency

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 Color blindness (color vision deficiency) is the decreased ability to see color or differences in color Color ( American English), or colour ( Commonwealth English), is the characteristic of visual perception described through color ...

color blind
'' (though this latter term can be misleading; almost all color deficient individuals can distinguish at least some colors). 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 Achromatopsia, also known as total color blindness, is a medical syndrome that exhibits symptoms relating to at least five conditions. The term may refer to acquired conditions such as cerebral achromatopsia, but it typically refers to an autosom ...
'') are caused by neural anomalies in those parts of the brain where visual processing takes place.


Tetrachromacy

While most humans are ''trichromatic'' (having three types of color receptors), many animals, known as '' tetrachromats'', have four types. These include some species of
spider Spiders (order (biology), order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude spider silk, silk. They are the largest order of arachnids and rank se ...

spider
s, most
marsupial Marsupials are any members of the mammalian Class (biology), infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are ...
s,
bird Birds are a group of warm-blooded vertebrates constituting the class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of indiv ...
s,
reptile Reptiles, as most commonly defined, are the animals in the Class (biology), class Reptilia , a paraphyletic grouping comprising all amniotes except synapsids (mammals and their extinct relatives) and Aves (birds). Living reptiles comprise turtle ...

reptile
s, and many species of
fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. Included in this definition are the living hagfish, lampreys, and Chondrichthyes, cartilaginous and bony fish as we ...

fish
. 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 are retinal tetrachromats. 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. To have two different genes, a person must have two X chromosomes, which is why the phenomenon only occurs in women. There is one scholarly report that confirms the existence of a functional tetrachromat.


Synesthesia

In certain forms of
synesthesia Synesthesia or synaesthesia is a perceptual phenomenon in which stimulation of one sensory or cognitive pathway leads to involuntary experiences in a second sensory or cognitive pathway. People who report a lifelong history of such experi ...

synesthesia
/
ideasthesia Ideasthesia (alternative spelling ideaesthesia) is a neuroscientific phenomenon in which activations of concepts (inducers) evoke perception-like sensory experiences (concurrents). The name comes from the Ancient Greek Ancient Greek inclu ...
, perceiving letters and numbers ( grapheme–color synesthesia) or hearing musical sounds (music–color synesthesia) will lead to the unusual additional experiences of seeing colors. Behavioral and
functional neuroimaging 240px, Functional magnetic resonance imaging data Functional neuroimaging is the use of neuroimaging Neuroimaging or brain imaging is the use of various techniques to either directly or indirectly Medical imaging, image the neuroanatomy, structu ...
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.


Afterimages

After exposure to strong light in their sensitivity range, s 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
afterimage An afterimage is an image that continues to appear in the eyes after a period of exposure to the original image. An afterimage may be a normal phenomenon (physiological afterimage) or may be pathological ( palinopsia). Illusory palinopsia may be ...
s, 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 color Color ( American English), or colour ( Commonwealth English), is the characteristic of visual perception described through color ''categories'', with names such as red, orange (colour), orange, ...

complementary color
. Afterimage effects have also been utilized by artists, including
Vincent van Gogh '', 1890. Van Gogh Museum, Amsterdam, alt= An expansive painting of a wheatfield, with a footpath going through the centre underneath dark and forbidding skies, through which a flock of black crows fly. Vincent Willem van Gogh (; 30 March 1 ...
.


Color constancy

When an artist uses a limited color palette, the
human eye The human eye is a organ (anatomy), sense organ that reacts to light and allows Visual perception, vision. Rod cell, Rod and Cone cell, cone cells in the retina are photoreceptive cells which are able to detect Light, visible light and convey thi ...

human eye
tends to compensate by seeing any gray or neutral color as the color which is missing from the color wheel. For example, 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 gray will appear bluish. The trichromatic theory is strictly true when the visual system is in a fixed state of adaptation. In reality, the visual system is constantly adapting to changes in the environment and compares the various colors in a scene to reduce 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 in the scene appear relatively constant to us. This was studied by Edwin H. Land in the 1970s and led to his retinex theory of
color constancy are recognized as being the same in sun and shade Image:ColourIllusion2.jpg, upright=1.2, In these two pictures, the second card from the left seems to be a stronger shade of pink in the upper one than in the lower one. In fact they are the ...
. Both phenomena are readily explained and mathematically modeled with modern theories of chromatic adaptation and color appearance (e.g.
CIECAM02 In colorimetry, CIECAM02 is the color appearance model published in 2002 by the International Commission on Illumination (CIE) Technical Committee 8-01 (''Color Appearance Modelling for Color Management Systems'') and the successor of Color appear ...
, iCAM).M.D. Fairchild
Color Appearance Models
, 2nd Ed., Wiley, Chichester (2005).
There is no need to dismiss the trichromatic theory of vision, but rather it can be enhanced with an understanding of how the visual system adapts to changes in the viewing environment.


Color naming

Colors vary in several different ways, including
hue In color theory, hue is one of the main properties (called color appearance parameters) of a color Color ( American English), or colour ( Commonwealth English), is the characteristic of visual perception described through color ''c ...

hue
(shades of
red Red is the color at the long wavelength end of the visible spectrum Laser beams with visible spectrum The visible spectrum is the portion of the electromagnetic spectrum that is visual perception, visible to the human eye. Electromagnetic ...

red
,
orange Orange most often refers to: *Orange (colour), occurs between red and yellow in the visible spectrum *Orange (fruit), the fruit of the tree species '' Citrus'' × ''sinensis'' ** Orange blossom, its fragrant flower *Some other citrus or citrus-li ...
,
yellow Yellow is the color Color ( American English), or colour ( Commonwealth English), is the characteristic of visual perception described through color ''categories'', with names such as red, orange (colour), orange, yellow, green, blue, ...

yellow
,
green Green is the color Color ( American English), or colour ( Commonwealth English), is the characteristic of visual perception described through color ''categories'', with names such as red, orange (colour), orange, yellow, green, b ...

green
,
blue Blue is one of the three primary colours of pigments in painting, drawing (art) and traditional colour theory, as well as in the RGB color model, RGB colour model. It lies between purple and green on the optical spectrum, spectrum of visible ...
, and
violet Violet may refer to: Common meanings * Violet (color), a spectral color with wavelengths shorter than blue * One of a list of plants known as violet, particularly: ** Viola (plant), ''Viola'' (plant), a genus of flowering plants Places United ...
), saturation,
brightness Brightness is an attribute of visual perception Visual perception is the ability to interpret the surrounding environment using light in the visible spectrum reflected by the objects in the environment (biophysical), environment. This is dif ...
, and gloss. Some color words are derived from the name of an object of that color, such as "
orange Orange most often refers to: *Orange (colour), occurs between red and yellow in the visible spectrum *Orange (fruit), the fruit of the tree species '' Citrus'' × ''sinensis'' ** Orange blossom, its fragrant flower *Some other citrus or citrus-li ...
" or "
salmon Salmon is the common name for several species of ray-finned fish in the family (biology), family Salmonidae. Other fish in the same family include trout, Salvelinus, char, Thymallus, grayling, and Freshwater whitefish, whitefish. Salmon are n ...
", while others are abstract, like "red". In the 1969 study '' Basic Color Terms: Their Universality and Evolution'',
Brent Berlin Overton Brent Berlin (born 1936) is an American anthropologistAn anthropologist is a person engaged in the practice of anthropology. Anthropology is the study of aspects of humans within past and present Society, societies. Social anthropology, cul ...
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). 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 yellow 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, gray, white, pink, red, orange, yellow, green, blue, purple, brown, and azure (distinct from blue in
Russian Russian refers to anything related to Russia, including: *Russians (русские, ''russkiye''), an ethnic group of the East Slavic peoples, primarily living in Russia and neighboring countries *Rossiyane (россияне), Russian language term ...
and
Italian Italian may refer to: * Anything of, from, or related to the country and nation of Italy ** Italians, an ethnic group or simply a citizen of the Italian Republic ** Italian language, a Romance language *** Regional Italian, regional variants of the ...

Italian
, but not English).


In culture

Colors, their meanings and associations can play major role in works of art, including literature.


Associations

Individual colors have a variety of cultural associations such as
national colorsNational colours are frequently part of a country's set of national symbols. Many states and nations have formally adopted a set of Color, colours as their official "national colours" while others have ''de facto'' national colours that have become ...
(in general described in individual color articles and
color symbolism Color symbolism in art Art is a diverse range of (products of) human activities involving creative imagination to express technical proficiency, beauty, emotional power, or conceptual ideas. There is no generally agreed definition of wha ...
). The field of color psychology attempts to identify the effects of color on human emotion and activity.
Chromotherapy Chromotherapy, sometimes called color therapy, colorology or cromatherapy, is an alternative medicine Alternative medicine is any practice that aims to achieve the healing effects of medicine Medicine is the Art (skill), art, science, and ...
is a form of
alternative medicine Alternative medicine is any practice that aims to achieve the healing effects of medicine Medicine is the Art (skill), art, science, and Praxis (process) , practice of caring for a patient and managing the diagnosis, prognosis, Preventive me ...
attributed to various Eastern traditions. Colors have different associations in different countries and cultures. Different colors have been demonstrated to have effects on cognition. For example, researchers at the University of Linz in Austria demonstrated that the color red significantly decreases cognitive functioning in men.


Spectral colors and color reproduction

Most light sources are mixtures of various wavelengths of light. Many such sources can still effectively produce a spectral color, as the eye cannot distinguish them from single-wavelength 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 cones to respond the way they do to the spectral color orange. A useful concept in understanding the perceived color of a non-monochromatic light source is the
dominant wavelength Image:dominant wavelength.png, frame, Dominant/complementary wavelength example on the CIE color spaceThe "x" marks the color in question. For the white point indicated, the dominant wavelength for "x" is on the nearer perimeter, around 600 nm, whi ...
, which identifies the single wavelength of light that produces a sensation most similar to the light source. Dominant wavelength is roughly akin to
hue In color theory, hue is one of the main properties (called color appearance parameters) of a color Color ( American English), or colour ( Commonwealth English), is the characteristic of visual perception described through color ''c ...

hue
. There are many color perceptions that by definition cannot be pure spectral colors due to
desaturation Desaturation may refer to: * In pulse oximetry, the condition of a low blood oxygen concentration * Reduction of colorfulness in image processing * Conversion of a saturated compound into an unsaturated compound by a removal of two hydrogen molecule ...
or because they are
purple Purple refers to any of a variety of colors with hue between red and blue. Purple is closely associated with Violet (color), violet. In optics, purple and violet refer to colors that look similar, but purples are mixtures of red light and b ...

purple
s (mixtures of red and violet light, from opposite ends of the spectrum). Some examples of necessarily non-spectral colors are the achromatic colors (black, gray, and white) and colors such as
pink Pink is the color of a namesake flower that is a pale tint of red. It was first used as a color name in the late 17th century. According to surveys in Europe and the United States, pink is the color most often associated with charm, politeness, ...

pink
, tan, and
magenta Magenta () is a colour that is variously defined as purplish-red, reddish-purple or mauve, mauvish-crimson. On color wheel, colour wheels of the RGB color model, RGB (additive) and subtractive color, CMY (subtractive) colour models, it is locate ...

magenta
. Two different light spectra that have the same effect on the three color receptors in the
human eye The human eye is a organ (anatomy), sense organ that reacts to light and allows Visual perception, vision. Rod cell, Rod and Cone cell, cone cells in the retina are photoreceptive cells which are able to detect Light, visible light and convey thi ...

human eye
will be perceived as the same color. They are metamers of that color. This is exemplified by the white light emitted by fluorescent lamps, which typically has a spectrum 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; for example, to make
fruit In botany, a fruit is the seed-bearing structure in flowering plants (also known as angiosperms) formed from the ovary after flowering. Fruits are the means by which angiosperms disseminate seeds. Edible fruits, in particular, have propa ...

fruit
or
tomato The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as a tomato plant. The species originated in western South America South America is a continent entirely in the Western Hemisphere and mostly in the ...

tomato
es look more intensely red.) 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 space A color space is a specific organization of colors. In combination with color profiling supported by various physical devices, it supports reproducible representations of color -- whether such representation entails an analog signal, analog or a ...
s for specifying a color in terms of three particular
primary colors A set of primary colors is a set of ''real'' colorants or colored lights that can be mixed in varying amounts to produce a gamut of colors. This is the essential method used in applications that are intended to elicit the perception of diverse ...

primary colors
. Each method has its advantages and disadvantages depending on the particular application. No mixture of colors, however, can produce a response truly identical to that of a spectral color, although one can get close, especially for the longer wavelengths, where the
CIE 1931 color space The CIE 1931 color spaces are the first defined quantitative links between distributions of wavelengths in the electromagnetic visible spectrum, and physiologically perceived colors in human color vision. The mathematical relationships that define ...
chromaticity diagram has a nearly straight edge. 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 Color printing or colour printing is the reproduction of an image or text in color (as opposed to simpler black and white or monochrome printing). Any natural scene or color photograph can be optically and physiologically dissected into three p ...
systems generally are not pure themselves, the colors reproduced are never perfectly saturated spectral 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 , displayed in the CIE 1931 chromaticity diagram The CIE 1931 color spaces are the first defined quantitative links between distributions of wavelengths in the electromagnetic visible spectrum, and physiologically perceived colors in human color ...
. The
CIE CIE may refer to: Organizations * Cambridge International Examinations, an international examination board * Center for International Education at the University of Massachusetts-Amherst * Cleveland Institute of Electronics, a private technical an ...
chromaticity diagram can be used to describe the gamut. 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 can be relatively poor if they have special, often very "jagged", spectra caused for example by unusual lighting of the photographed scene. A color reproduction system "tuned" to a human with normal color vision may give very inaccurate results for other observers. The different color response of different devices can be problematic if not properly managed. For color information stored and transferred in digital form,
color management In digital imaging systems, color management (or colour management) is the controlled conversion between the color Color ( American English), or colour ( Commonwealth English), is the characteristic of visual perception described throug ...
techniques, such as those based on
ICC profile 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 International Color Consortium (ICC). Profiles describe the color attributes of a ...
s, can help to avoid distortions of the reproduced colors. Color management does not circumvent the gamut limitations of particular output devices, but can assist in finding good mapping of input colors into the gamut that can be reproduced.


Additive coloring

Additive color James Clerk Maxwell, with his color top that he used for investigation of color vision and additive color Additive color or additive mixing is a property of a color model that predicts the appearance of color Color ( American English), ...
is light created by mixing together
light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that can be visual perception, perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 ...

light
of two or more different colors.
Red Red is the color at the long wavelength end of the visible spectrum Laser beams with visible spectrum The visible spectrum is the portion of the electromagnetic spectrum that is visual perception, visible to the human eye. Electromagnetic ...

Red
,
green Green is the color Color ( American English), or colour ( Commonwealth English), is the characteristic of visual perception described through color ''categories'', with names such as red, orange (colour), orange, yellow, green, b ...

green
, and
blue Blue is one of the three primary colours of pigments in painting, drawing (art) and traditional colour theory, as well as in the RGB color model, RGB colour model. It lies between purple and green on the optical spectrum, spectrum of visible ...
are the additive
primary color A set of primary colors is a set of ''real'' colorants or colored lights that can be mixed in varying amounts to produce a gamut of colors. This is the essential method used in applications that are intended to elicit the perception of diverse s ...
s normally used in additive color systems such as projectors and computer terminals.


Subtractive coloring

Subtractive color Subtractive color or subtractive color mixing predicts the spectral power distribution In radiometry, photometry (optics), photometry, and color science, a spectral power distribution (SPD) measurement describes the Power (physics), power per u ...
ing uses dyes, inks, pigments, or filters to absorb some wavelengths of light and not others. The color that a surface displays comes from the parts of the visible spectrum that are not absorbed and therefore remain visible. Without pigments or dye, fabric fibers, paint base and paper are usually made of particles that scatter white light (all colors) well in all directions. When a pigment or ink is added, wavelengths are absorbed or "subtracted" from white light, so light of another color reaches the eye. If the light is not a pure white source (the case of nearly all forms of artificial lighting), the resulting spectrum will appear a slightly different color.
Red Red is the color at the long wavelength end of the visible spectrum Laser beams with visible spectrum The visible spectrum is the portion of the electromagnetic spectrum that is visual perception, visible to the human eye. Electromagnetic ...

Red
paint, viewed under
blue Blue is one of the three primary colours of pigments in painting, drawing (art) and traditional colour theory, as well as in the RGB color model, RGB colour model. It lies between purple and green on the optical spectrum, spectrum of visible ...
light, may appear
black Black is a color which results from the absence or complete absorption of visible light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that can be visual perception, perceived by t ...
. Red paint is red because it scatters only the red components of the spectrum. If red paint is illuminated by blue light, it will be absorbed by the red paint, creating the appearance of a black object.


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 one or more parallel thin layers, or otherwise composed of microstructures on the scale of the color's
wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase (waves), phase on the wave, such as two adjac ...

wavelength
. If the microstructures are spaced randomly, light of shorter wavelengths will be scattered preferentially to produce colors: the blue of the sky (Rayleigh scattering, caused by structures much smaller than the wavelength of light, in this case air molecules), the luster of
opal Opal is a hydrated amorphous form of Silicon dioxide, silica (SiO2·''n''H2O); its water content may range from 3 to 21% by weight, but is usually between 6 and 10%. Because of its amorphous character, it is classed as a mineraloid, unlike cr ...

opal
s, and the blue of human irises. If the microstructures are aligned in arrays, for example the array of pits in a CD, they behave as a
diffraction grating In optics Optics is the branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (phy ...
: the grating reflects different wavelengths in different directions due to
interference Interference is the act of interfering, invading, or poaching. Interference may also refer to: Communications * Interference (communication), anything which alters, modifies, or disrupts a message * Adjacent-channel interference, caused by extran ...

interference
phenomena, separating mixed "white" light into light of different wavelengths. 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 studied in the field of
thin-film optics A pattern of coloured light formed by interference between white light being reflected from the surface of a thin film of diesel fuel on the surface of water, and the diesel-water interface. Thin-film optics is the branch of optic Optics is ...
. The most ordered or the most changeable structural colors are
iridescent Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear to Gradient, gradually change color as the angle of view or the angle of illumination changes. Examples of iridescence include soap bubbles, feathers, ...
. 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 Peafowl is a common name for three bird species in the genera ''Pavo (genus), Pavo'' and ''Afropavo'' of the family Phasianidae, the pheasants and their allies. Male peafowl are referred to as peacocks, and female peafowl are referred to as pe ...

peacock
feathers,
soap bubble A soap bubble is an extremely thin soap film, film of soapy water enclosing air that forms a hollow sphere with an iridescent surface. Soap bubbles usually last for only a few seconds before bursting, either on their own or on contact with anot ...
s, films of oil, and
mother of pearl Nacre ( also ), also known as mother of pearl, is an organicinorganic composite material A composite material (also called a composition material or shortened to composite, which is the common name) is a material which is produced from two or ...

mother of pearl
, because the reflected color depends upon the viewing angle. Numerous scientists have carried out research in butterfly wings and beetle shells, including Isaac Newton and Robert Hooke. Since 1942, has been used, advancing the development of products that exploit structural color, such as "
photonic Photonics is the optics, physical science and application of light (photon) generation, detection, and manipulation through Emission (electromagnetic radiation), emission, Transmission (telecommunications), transmission, modulation, signal proces ...
" cosmetics.


Additional terms

*
Color wheel A color wheel or color circle is an abstract illustrative organization of color Color ( American English), or colour ( Commonwealth English), is the characteristic of visual perception described through color ''categories'', with names ...
: an illustrative organization of color hues in a circle that shows relationships. *
Colorfulness File:Saturation of digital colors.png, 300x300px, 7.5PB and 10BG Munsell hue pages of RGB colors, showing lines of uniform saturation (chroma in proportion to lightness) in red. Note that lines of uniform saturation radiate from near the black ...
, chroma, purity, or saturation: how "intense" or "concentrated" a color is. Technical definitions distinguish between colorfulness, chroma, and saturation as distinct perceptual attributes and include purity as a physical quantity. These terms, and others related to light and color are internationally agreed upon and published in the CIE Lighting Vocabulary. More readily available texts on colorimetry also define and explain these terms.R.S. Berns
Principles of Color Technology
, 3rd Ed., Wiley, New York (2001).
* Dichromatism: a phenomenon where the hue is dependent on concentration and thickness of the absorbing substance. *
Hue In color theory, hue is one of the main properties (called color appearance parameters) of a color Color ( American English), or colour ( Commonwealth English), is the characteristic of visual perception described through color ''c ...

Hue
: the color's direction from white, for example in a
color wheel A color wheel or color circle is an abstract illustrative organization of color Color ( American English), or colour ( Commonwealth English), is the characteristic of visual perception described through color ''categories'', with names ...
or
chromaticity Chromaticity is an objective specification of the quality of a color regardless of its luminance. Chromaticity consists of two dimension (mathematics and physics), independent parameters, often specified as hue (h) and colorfulness (s), where th ...
diagram. * Shade: a color made darker by adding black. *
Tint In color theory, a tint is a mixture of a color with white, which increases lightness, while a shade is a mixture with black, which increases darkness. Both processes affect the resulting color mixture's relative Colorfulness#Saturation, saturat ...
: a color made lighter by adding white. *
Value Value or values may refer to: * Value (ethics) it may be described as treating actions themselves as abstract objects, putting value to them ** Values (Western philosophy) expands the notion of value beyond that of ethics, but limited to Western s ...

Value
, brightness, lightness, or luminosity: how light or dark a color is.


See also

*
Chromophore A chromophore is the part of a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral group of two o ...
*
Color analysis (art) Color analysis (American English; colour analysis in Commonwealth English), also known as personal color analysis (PCA), seasonal color analysis, or skin-tone matching, is a term often used within the cosmetics and fashion industry to describe a ...
*Color mapping *Complementary color *Impossible color *International Color Consortium *International Commission on Illumination *Lists of colors list of colors (compact), (compact version) *Neutral color *Pearlescent coating including Metal effect pigments *Primary color, Primary, secondary color, secondary and tertiary colors


References


External links


ColorLab
MATLAB toolbox for color science computation and accurate color reproduction (by Jesus Malo and Maria Jose Luque, Universitat de Valencia). It includes CIE standard tristimulus colorimetry and transformations to a number of non-linear color appearance models (CIE Lab, CIE CAM, etc.).

Buenos Aires University * * *Robert Ridgway'
''A Nomenclature of Colors'' (1886)
an
''Color Standards and Color Nomenclature'' (1912)
text-searchable digital facsimiles at Linda Hall Library *Albert Henry Munsell'
''A Color Notation''
(1907) at Project Gutenberg
AIC
International Colour Association
The Effect of Color , OFF BOOK
Documentary produced by Off Book (web series), Off Book
Study of the history of colorsDon Dedrick: "Colour classification in natural languages". In ISKO Encyclopedia of Knowledge Organization
{{Authority control Color, Image processing Qualia Vision