Color

Color is a property of light that depends on the frequency of light waves. Frequency is defined as the number of wave segments that pass a given point every second. In most cases, when people talk about light, they are referring to white light. The best example of white light is ordinary sunlight: light that comes from the Sun.

Light is a form of electromagnetic radiation: a form of energy carried by waves. The term "electromagnetic radiation" refers to a vast range of energy waves, including gamma rays, X rays, ultraviolet rays, visible light, infrared radiation, microwaves, radar, and radio waves. Of all these forms, only one can be detected by the human eye: visible light.

White light and color

White light (such as sunlight) and colors are closely related. A piece of glass or crystal can cause a beam of sunlight to break up into a rainbow: a beautiful separation of colors. The technical term for a rainbow is a spectrum. The colors in a spectrum range from deep purple to brilliant red. One way to remember the colors of the spectrum is with the mnemonic device (memory clue) ROY G. BIV, which stands for Red, Orange, Yellow, Green, Blue, Indigo, and Violet.

English physicist Isaac Newton (1642–1727) was the first person to study the connection between white light and colors. Newton caused a beam of white light to fall on a glass prism and found that the white light was broken up into a spectrum. He then placed a second prism in front of the first and found that the colors could be brought back together into a beam of white light. A rainbow is a naturally occurring illustration of Newton's experiment. Instead of a glass prism, though, it is tiny droplets of rainwater that cause sunlight to break up into a spectrum of colors, a spectrum we call a rainbow.

Color and wavelength

The word "color" actually refers to the light of a particular color, such as red light, yellow light, or blue light. The color of a light beam depends on just one factor: the wavelength of the light. Wavelength is defined as the distance between two exactly identical parts of a given wave. Red light consists of light waves with a wavelength of about 700 nanometers (billionths of a meter), yellow light has wavelengths of about 550 nanometers, and blue light has wavelengths of about 450 nanometers. But the wavelengths of colored light are not limited to specific ranges. For example, waves that have wavelengths of 600, 625, 650, and 675 nanometers would have orange, orangish-red, reddish-orange, and, finally, red colors.

Words to Know

Color: A property of light determined by its wavelength.

Colorant: A chemical substance—such as ink, paint, crayons, or chalk—that gives color to materials.

Complementary colors: Two colors that, when mixed with each other, produce white light.

Electromagnetic radiation: A form of energy carried by waves.

Frequency: The number of segments in a wave that pass a given point every second.

Gray: A color produced by mixing white and black.

Hue: The name given to a color on the basis of its frequency.

Light: A form of energy that travels in waves.

Nanometer: A unit of length; this measurement is equal to one-billionth of a meter.

Pigment: A substance that displays a color because of the wavelengths of light that it reflects.

Primary colors: Colors that, when mixed with each other, produce white light.

Shade: The color produced by mixing a color with black.

Spectrum: The band of colors that forms when white light is passed through a prism.

Tint: The color formed by mixing a given color with white.

Tone: The color formed by mixing a given color with gray (black and white).

Wavelength: The distance between two exactly identical parts of a wave.

The color of objects

Light can be seen only when it reflects off some object. For example, as you look out across a field, you cannot see beams of light passing through the air, but you can see the green of trees, the brown of fences, and the yellow petals of flowers because of light reflected by these objects.

To understand how objects produce color, imagine an object that reflects all wavelengths of light equally. When white light shines on that object, all parts of the spectrum are reflected equally. The color of the object is white. (White is generally not regarded as a color but as a combination of all colors mixed together.)

Now imagine that an object absorbs (soaks up) all wavelengths of light that strike it. That is, no parts of the spectrum are reflected. This object is black, a word that is used to describe an object that reflects no radiation.

Finally, imagine an object that reflects light with a wavelength of about 500 nanometers. Such an object will absorb all wavelengths of light except those close to 500 nanometers. It will be impossible to see red light (700 nanometers), violet light (400 nanometers), or blue light (450 nanometers) because those parts of the spectrum are all absorbed by the object. The only light that is reflected—and the only color that can be seen—is green, which has a wavelength of about 500 nanometers.

Primary and complementary colors

White light can be produced by combining all colors of the spectrum at once, as Newton discovered. However, it is also possible to make white light by combining only three colors in the spectrum: red, green, and blue. For this reason, these three colors of light are known as the primary colors. (For more on the concept of primary colors, see subhead titled "Pigments.") In addition to white light, all colors of the spectrum can be produced by an appropriate mixing of the primary colors. For example, red and green lights will combine to form yellow light.

It is also possible to make white light by combining only two colors, although these two colors are not primary colors. For example, the combination of a bluish-violet light and a yellow light form white light. Any two colors that produce white light, such as bluish-violet and yellow, are known as complementary colors.

The language of colors

A special vocabulary is used to describe colors. The fundamental terms include:

Hue: The basic name of a color, as determined by its frequency. Light with a wavelength of 600 nanometers is said to have an orange hue.

Gray: The color produced by mixing white and black.

Shade: The color produced by mixing a color with black. For example, the shade known as maroon is formed by mixing red and black.

Tint: The color formed by mixing a color with white. Pink is produced when red and white are mixed.

Tone: The color formed by mixing a color with gray (black and white). Red plus white plus black results in the tone known as rose.

Pigments

A pigment is a substance that reflects only certain wavelengths of light. Strictly speaking, there is no such thing as a white pigment because such a substance would reflect all wavelengths of light. A red pigment is one that reflects light with a wavelength of about 700 nanometers; a blue pigment is one that reflects light with a wavelength of about 450 nanometers.

The rules for combining pigment colors are different from those for combining light colors. For example, combining yellow paint and blue paint produces green paint. Combining red paint with yellow paint produces orange paint. And combining all three of the primary colors of paints—yellow, blue, and red—produces black paint.

Other color phenomena

Color effects occur in many different situations in the natural world. For example, the swirling colors in a soap bubble are produced by interference, a process in which light is reflected from two different surfaces very close to each other. The soap bubble is made of a very thin layer of soap: the inside and outside surfaces are less than a millimeter away from each other. When light strikes the bubble, then, it is reflected from both the outer surface and from the inside surface of the bubble. The two reflected beams of light interfere with each other in such a way that some wavelengths of light are reinforced, while others are canceled out. It is by this mechanism that the colors of the soap bubble are produced.

[See also Light; Spectroscopy ]

92. Color

achromaticity

1. the total absence of color.

2. the ability to emit, reflect, or transmit light without breaking down into separate colors. Also achromatism.

achromatopsy, achromatopsia

color blindness. Also called acritochromacy .

acyanoblepsia

a variety of color blindness characterized by an inability to distinguish blue.

albescence

the condition of being or becoming white or whitish. —albescent , adj.

albication

the process of turning white or whitish.

chatoyancy

the condition or quality of changing in color or luster depending on the angle of light, exhibited especially by a gemstone that reflects a single shaft of light when cut in cabochon form. —chatoyant , adj.

chromatics

the branch of opties that studies the properties of colors.

chromatism

1. Opties, dispersion or distortion of color.

2. abnormal coloration. See also 54. BOTANY .

chromatology

the study of colors. Also called chromatography .

chromatrope

an instrument consisting of an arrangement of colored dises which, when rotated rapidly, give the impression of colors flowing to or from the center.

chromophobia

an abnormal fear of colors.

chromoptometer

a device for measuring the degree of a person’s sense of color.

chromotypography, chromotypy

the process of color printing.

colorimetry

the measurement of the physical intensity of colors, as opposed to their subjective brightness. —colorimeter , n. —colorimetric, colorimetrical , adj.

cyanometry

the measurement of the intensity of the sky’s blue color. —cyanometer , n. —cyanometric , adj.

Daltonism

red-green color blindness.

deuteranopia

a defect of the eyesight in which the retina does not respond to green. —deuteranope , n. —deuteranopic , adj.

dichroism

a property, peculiar to certain crystals, of reflecting light in two different colors when viewed from two different directions. —dichroic , adj.

dichromatism

1. the quality of being dichromatic, or having two colors.

2. a form of color blindness in which the sufferer can perceive only two of the three primary colors and their variants. —dichromatic , adj.

dyschromatopsia

difficulty in telling colors apart; color blindness.

erythrophobia

an abnormal fear of the color red.

floridity

the condition of being florid or highly colored, especially reddish, used especially of the complexion. —florid , adj.

glaucescence

1. the state or quality of being a silvery or bluish green in color.

2. the process of turning this color. —glaucescent , adj.

hyperchromatism

the occurrence of unusually intense coloration. —hyperchromatic , adj.

indigometer

an instrument used for determining the strength of an indigo solution.

indigometry

the practice and art of determining the strength and coloring power of an indigo solution.

iridescence

the state or condition of being colored like a rainbow or like the light shining through a prism. —iridescent , adj.

irisation

the process of making or becoming iridescent.

iriscope

a polished black glass, the surface of which becomes iridescent when it is breathed upon through a tube.

melanoscope

an optical device composed of red and violet glass that transmits red light only, used for distinguishing red in varicolored flames.

metachromatism

change in color, especially as a result of change in temperature.

monochromatism

1. the quality of being of only one color or in only one color, as a work of art.

2. a defect of eyesight in which the retina cannot perceive color. —monochromatic , adj.

mordancy, mordacity

the property of acting as a flxative in dyeing. — mordant, n., adj.

opalescence

the quality of being opallike, or milkily iridescent. —opalescent , adj.

pallidity

a faintness or deficiency in color. —pallid , adj.

panchromatism

the quality or condition of being lsensitive to all colors, as certain types of photographic film. —panchromatic , adj.

polychromatism

the state or quality of being multicolored. —polychromatic, polychromie , adj.

protanopia

a defect of the eyesight in which the retina does not respond to red. —protanope , n. —protanopic , adj.

rubescence

1. the state, condition, quality, or process of becoming or being red.

2. a blush.

3. the act of blushing. —rubescent , adj.

rufescence

1. the tendency to turn red or reddish.

2. reddishness. —rufescent , adj.

spectrogram

a photograph of a spectrum. Also called spectrograph .

spectrograph

1. an optical device for breaking light down into a spectrum and recording the results photographically.

2. a spectrogram. —spectrographic , adj.

spectrography

the technique of using a spectrograph and producing spectrograms.

trichroism

a property, peculiar to certain crystals, of transmitting light of three different colors when viewed from three different directions. Also trichromatism . —trichroic , adj.

trichromatism

1. the condition of having, using, or combining three colors.

2. trichroism. —trichromatic , adj.

tritanopia

a defect of the eyesight in which the retina does not respond to blue and yellow. —tritanope , n. —tritanopic , adj.

verdancy

the quality or condition of being green, as the condition of being covered with green plants or grass or inexperience attributable to youth. —verdant , adj.

viridescence

1. the state or quality of being green or greenish.

2. greenishness. —viridescent , adj.

xanthocyanopsy, xanthocyanopy

a form of color blindness in which only yellow and blue can be perceived.

color effect produced on the eye and its associated nerves by light waves of different wavelength or frequency. Light transmitted from an object to the eye stimulates the different color cones of the retina, thus making possible perception of various colors in the object.

See also light ; painting ; protective coloration ; vision .

The Visible Spectrum

Since the colors that compose sunlight or white light have different wavelengths, the speed at which they travel through a medium such as glass differs; red light, having the longest wavelength, travels more rapidly through glass than blue light, which has a shorter wavelength. Therefore, when white light passes through a glass prism , it is separated into a band of colors called a spectrum . The colors of the visible spectrum, called the elementary colors, are red, orange, yellow, green, blue, indigo, and violet (in that order).

Apparent Color of Objects

Color is a property of light that depends on wavelength. When light falls on an object, some of it is absorbed and some is reflected. The apparent color of an opaque object depends on the wavelength of the light that it reflects; e.g., a red object observed in daylight appears red because it reflects only the waves producing red light. The color of a transparent object is determined by the wavelength of the light transmitted by it. An opaque object that reflects all wavelengths appears white; one that absorbs all wavelengths appears black. Black and white are not generally considered true colors; black is said to result from the absence of color, and white from the presence of all colors mixed together.

Additive Colors

Colors whose beams of light in various combinations can produce any of the color sensations are called primary, or spectral, colors. The process of combining these colors is said to be "additive" ; i.e., the sensations produced by different wavelengths of light are added together. The additive primaries are red, green, and blue-violet. White can be produced by combining all three primary colors. Any two colors whose light together produces white are called complementary colors, e.g., yellow and blue-violet, or red and blue-green.

Subtractive Colors

When pigments are mixed, the resulting sensations differ from those of the transmitted primary colors. The process in this case is "subtractive," since the pigments subtract or absorb some of the wavelengths of light. Magenta (red-violet), yellow, and cyan (blue-green) are called subtractive primaries, or primary pigments. A mixture of blue and yellow pigments yields green, the only color not absorbed by one pigment or the other. A mixture of the three primary pigments produces black.

Properties of Colors

The scientific description of color, or colorimetry, involves the specification of all relevant properties of a color either subjectively or objectively. The subjective description gives the hue, saturation, and lightness or brightness of a color. Hue refers to what is commonly called color, i.e., red, green, blue-green, orange, etc. Saturation refers to the richness of a hue as compared to a gray of the same brightness; in some color notation systems, saturation is also known as chroma. The brightness of a light source or the lightness of an opaque object is measured on a scale ranging from dim to bright for a source or from black to white for an opaque object (or from black to colorless for a transparent object). In some systems, brightness is called value. A subjective color notation system provides comparison samples of colors rated according to these three properties. In an objective system for color description, the corresponding properties are dominant wavelength, purity, and luminance. Much of the research in objective color description has been carried out in cooperation with the Commission Internationale de l'Eclairage (CIE), which has set standards for such measurements. In addition to the description of color according to these physical and psychological standards, a number of color-related physiological and psychological phenomena have been studied. These include color constancy under varying viewing conditions, color contrast, afterimages, and advancing and retreating colors.

Symbolic Uses of Color

Color has long been used to represent affiliations and loyalties (e.g., school or regimental colors) and as a symbol of various moods (e.g., red with rage) and qualities (e.g., worthy of a blue ribbon). A well-known use of the symbolism of color is in the liturgical colors of the Western Church, according to which the color of the vestments varies through the ecclesiastical calendar; e.g., purple (i.e., violet) is the color of Advent and Lent; white, of Easter; and red, of the feasts of the martyrs.

Bibliography

See G. Wyszecki and W. S. Stiles, Color Science (1967); M. W. Levine and J. M. Shefner, Fundamentals of Sensation and Perception (1991).

col·or / ˈkələr/ (Brit. col·our) • n. 1. the property possessed by an object of producing different sensations on the eye as a result of the way the object reflects or emits light. ∎  one, or any mixture, of the constituents into which light can be separated in a spectrum or rainbow, sometimes including (loosely) black and white. ∎  the use of all colors, not only black, white, and gray, in photography or television: he has shot the whole film in color | [as adj.] color television. ∎  a substance used to give something a particular color: lip color. ∎ fig. a shade of meaning: many events in her past had taken on a different color. ∎ fig. character or general nature: the hospitable color of his family. ∎ Heraldry any of the major conventional colors used in coats of arms (gules, vert, sable, azure, purpure), esp. as opposed to the metals, furs, and stains. 2. the appearance of someone's skin; in particular: ∎  pigmentation of the skin, esp. as an indication of someone's race: discrimination on the basis of color. ∎  a group of people considered as being distinguished by skin pigmentation: all colors and nationalities. ∎  rosiness of the complexion, esp. as an indication of someone's health. ∎  redness of the face as a manifestation of an emotion, esp. embarrassment or anger. 3. vividness of visual appearance resulting from the presence of brightly colored things: for color, plant groups of winter-flowering pansies. ∎ fig. picturesque or exciting features that lend a particularly interesting quality to something. ∎  fig. variety of musical tone or expression: orchestral color. 4. (colors) an item or items of a particular color or combination of colors worn to identify an individual or a member of a school, group, or organization; in particular: ∎  the clothes or accoutrements worn by a jockey or racehorse to indicate the horse's owner. ∎  the flag of a regiment or ship. ∎  a national flag. ∎  the armed forces of a country, as symbolized by its flag: he was called to the colors during the war. 5. Physics a quantized property of quarks which can take three values (designated blue, green, and red) for each flavor. 6. Mining a particle of gold remaining in a mining pan after most of the mud and gravel have been washed away. • v. 1. [tr.] change the color of (something) by painting or dyeing it with crayons, paints, or dyes. ∎  [intr.] take on a different color: the foliage will not color well if the soil is too rich. ∎  use crayons to fill (a particular shape or outline) with color. ∎ fig. make vivid or picturesque. 2. [intr.] (of a person or their skin) show embarrassment or shame by becoming red; blush: everyone stared at him, and he colored slightly. ∎  [tr.] cause (a person or their skin) to change in color: rage colored his pale complexion. ∎  [tr.] (of a particular color) imbue (a person's skin): a pink flush colored her cheeks. ∎  [tr.] fig. (of an emotion) imbue (a person's voice) with a particular tone. 3. [tr.] influence, esp. in a negative way; distort: the experiences had colored her whole existence. ∎  misrepresent by distortion or exaggeration: witnesses might color evidence to make a story saleable. PHRASES: person of color see person of color. show one's true colors reveal one's real character or intentions, esp. when these are disreputable or dishonorable. with flying colors see flying.

COLOR

The appearance or semblance of a thing, as distinguished from the thing itself.

The thing to which the term color is applied does not necessarily have to possess the character imputed to it. A person who holds land under color of title does not have actual title to it.

color n.
1. the flag of a regiment or ship.

2. a national flag.

3. the armed forces of a country, as symbolized by its flag: he was called to the colors during the war.

color •colour (US color), cruller, culler, medulla, mullah, Muller, nullah, sculler, Sulla •doubler, troubler •bumbler, grumbler, stumbler, tumbler •bundler • muffler • juggler • bungler •suckler • coupler •hustler, rustler •butler, cutler •puzzler • swashbuckler • technicolor •multicolour (US multicolor) •watercolour (US watercolor)