Introduction to Color
Color, a class of sensations made by light on the optic nerve. All colors—whether seen in nature or applied by man with pigments through painting, dyeing, or printing—are caused by light and the way light affects the eyes.
Color and Light
Light is a form of radiant energy. It consists of short, rapid electromagnetic vibrations, or waves. In general, the eye sees different wavelengths of light as different colors. Sunlight contains virtually all wavelengths of light and therefore contains virtually all colors.
A prism will break down sunlight into its component wavelengths, forming an array of colored light known as the visible spectrum. (Drops of water do the same thing in creating a rainbow.) The normal human eye usually recognizes six bands of colors in the spectrum—violet, blue, green, yellow, orange, and red. The approximate range of wavelengths of light that make up the spectrum—from the extreme violet end to the extreme red end—is from 0.0004 to 0.00076 millimeters. The eye can see light of wavelengths somewhat beyond this range, but its sensitivity to this light is very weak.
Color and Objects
The color of any object depends on two things: (1) the kind of light that shines on the object, and (2) the kind of light that bounces off or passes through the object. Stated another way, color depends on which wavelengths reach the object and which wavelengths reach the eye after being reflected or transmitted by the object.
When light shines on an opaque object—an object that light will not pass through, such as a card, a wall, or a plum—some wavelengths will be absorbed by the object and some will be reflected. The chemical makeup of the surface of the object—that is, the pigments it contains—determines which wavelengths (and hence which colors) are reflected and which are absorbed.
A surface that reflects sunlight (which contains all colors) without absorbing any of its colors is said to be white. A surface that absorbs all colors, reflecting none, is said to be black. Weak vibrations of white light result in the sensation known as gray. An opaque object that appears blue absorbs all colors but blue; the blue light is reflected to the eye, giving the object its color. A "red" object reflects only red light, a "green" object reflects only green, and so on.
The color of an opaque object can be changed by coating its surface with paints, dyes, inks, or other coloring matter. The pigments in these agents determine which colors will be absorbed and which will be reflected.
Transparent objects do not reflect light, but transmit it. Therefore the color of such an object depends on the color of the light that passes through it. Ordinary window glass transmits all colors and is said to have no color of its own. "Blue" glass transmits only blue light, absorbing all other colors. Here again, it is the chemical makeup of the substance that determines which colors will pass through and which will not.
Some substances do not contain pigments and yet still appear to have color. The sky is an example. As sunlight strikes the upper atmosphere, it is scattered by the air molecules. Blue light is scattered the most and illuminates the whole sky, giving it its color.
While sunlight contains all colors, artificial light does not. Therefore an object under an electric light does not receive the same kind of color as it does in sunlight—and it may seem to be a different color. To take an extreme example, an apple that appears red in sunlight will look black under green light—light that contains no color but green. This is because the apple can reflect only red light; since none is present, the apple absorbs all the light it receives and appears black.
Black, gray, and white are sometimes called neutral or achromatic colors; the other colors—blue, green, red, etc—are called chromatic.
Characteristics of Color
The eye can recognize three characteristics of color—hue, intensity, and value.
Hueis the identity of a color. When we say a color is blue, green, blue-green, or yellow, we are describing its hue. Hue does not refer to a color's lightness, darkness, or grayness.
Intensity, or Chroma,refers to the purity of a color—how close it is to being a single wavelength only. A saturated color—one that is absolutely free of all other colors—is rare, except in the laboratory. Most of the colors of common, everyday experience are a mixture of light of various wavelengths.
Valueis the lightness or darkness of a color. It indicates the amount of energy of the light making up the color. Increasing the brightness of a hue by adding white creates a tint. Black added to the hue will decrease the brightness, creating a shade. A tone is a color consisting of a hue with both white and black.
Primary Colors
Primary colors are any three colors that, when mixed in proper proportions, will produce a wide range of colors. (The common belief that all colors can be produced by a mixture of three properly chosen "primary colors" is incorrect.) There are two types—additive primaries (also called light, or optical, primaries) and subtractive, or pigment, primaries.
Additive PrimariesThe additive primaries—the primary colors of light—can be any three light beams of equal intensity that will combine to make white light. Orange-red (commonly called red), green, and violet-blue (commonly called blue) are usually considered to be the additive primaries, since their combination gives the maximum range of colors. By varying the intensities of the primaries in different combinations, it is possible to produce virtually any color.
This principle is the basis of a theory of color perception developed by Thomas Young (17731829) and Hermann von Helmholtz (18211894). According to this theory, the retina of the eye has three sets of color-sensitive cells, each set sensitive to one of the optical primaries. When the green set is stimulated by green light entering the eye, we see green; the same is true for blue and red. Other color sensations can be produced by proper stimulation of these sets of cells. Although experiments in the 1950's showed color vision to be more complex than this, in 1964 the three-color theory was proved essentially correct.
Subtractive, or Pigment, PrimariesThe pigment colors are the colors seen when one looks at an opaque object. They are the colors caused by partial absorption of white light. They are called subtractive because the colors they absorb are subtracted from the light they reflect.
The pigment colors that absorb the light of the additive primary colors are called the pigment primaries. These are the primary colors of the artist and printer. They are magenta (a reddish-purple shade), which absorbs green; yellow, which absorbs violet-blue; and cyan (a greenish blue), which absorbs orange-red. When all three pigments are mixed in equal proportions, the result is black or near black.
Various mixtures of these primaries will result in almost any color desired. For example, if cyan pigment is mixed with yellow pigment, green is produced. The cyan pigment absorbs, or subtracts, red and yellow light. The yellow pigment subtracts blue and violet. The only color not subtracted is green.
Secondary Colors
These are colors that can be produced by a mixture of equal parts of two primaries. A mixture of yellow and cyan pigments, for example, makes green; green is therefore a pigment secondary color. The primary colors of light are the secondary colors of pigment, and the primary colors of pigment are the secondary colors of light. All six colors—the primaries and secondaries—are seen in the spectrum or rainbow.
Complementary Colors
Any two contrasting colors that make a neutral color when added together are called complementary. Complementary colors are as far apart in hue as possible and are opposites on the color wheel. When complementary colors (red and green, for example) are placed next to each other, their hue seems to be heightened.
If the eyes gaze at a bright red spot for a minute or more, the retinas become saturated with red. If the eyes are then focused on a white surface, they subtract red from the white light and see green—the complement of red. This effect is called afterimage, or retinal fatigue. The afterimage is always complementary to the color with which the eyes have been saturated.
Color Harmony
Some colors go well together, others do not. The blending of colors into an attractive relationship is not simp]y a matter of personal taste, but is based on objective principles. An understanding of these principles is essential to artists, interior decorators, industrial designers, and others who must work with color. It is also very helpful to us all in choosing our clothes and decorating our homes.
A basic principle of color harmony is that one color must be stronger than the others, either in intensity or in the area covered. If two hues of equal intensity are placed side by side, they tend to compete for attention. The eye cannot focus on both, and they seem to vibrate. This effect is especially noticeable with two complementaries, such as pure red and pure green.
Another principle is that the colors must bear some relationship to each other. The color wheel is a useful tool for determining relationships. Colors that are side-by-side on the wheel—such as yellow and yellow green—will harmonize well. Complementary colors—colors directly across the wheel from one another—also go well together. Color triads—three colors equally spaced on the wheel, such as the three primaries—are also pleasing together. Tints, shades, and tones of the same color will never clash, but are usually effective only when there is a marked contrast between them.
It is always safe to use a single color with a neutral—a black, white or gray. Colors can be used in almost any combination if all the colors are subdued, containing large amounts of gray. The general effect, however, tends to be dull.
Color and Man
How Colors Affect UsColor sensations usually make their impact on the unconscious mind. Consequently people are often unaware of the tremendous influence colors have upon them. A person may be unconscious of the colors around him and yet be powerfully affected by them in regard to mood, temperament, and behavior.
Color sensations can produce physical reactions. People often feel cold in a blue room and warm in a red room without realizing that colors, not physical temperature, are responsible for the difference in effects. Colors derived from blue—the "cool" colors—have a sedative effect and have proved calming to highly nervous people. Less excitable people may become depressed in surroundings of strong blue and have their spirits lifted by "warm" colors—those derived from reds and yellows. Most people have a strong unconscious tendency to seek a balance of calming and stimulating colors by surrounding themselves with tints and tones derived from both cool and warm hues.
Our preference for a color depends not only on its tonal value, but also on how well it harmonizes with other colors around it. The amount of surface covered by a color also affects our feeling about it. A bright red wall might be disturbing, but the same color, if limited to small areas, can be quite pleasing. Certain colors are associated with certain objects, and the "wrong" color can be startling, unpleasant, or offensive. For example, green egg yolks look unappetizing because yellow is normally associated with yolks. Careful attention must be paid to the painting and lighting of dining rooms to prevent good food from being "spoiled" by the color of the room.
Practical Uses of ColorSince color affects people in definite ways, wise use of color in interior decorating is important. The color of a room should be chosen for its psychological effect—the mood it creates—and for its harmony with objects in the room. Color also has an important effect on illumination. Rooms that receive little sunlight should have light-colored walls and ceilings, which reflect a high percentage of light.
Color is widely used to attract attention, as in signs, advertisements, or danger signals. Fire-fighting equipment is red or yellow, and stop lights are red. The highly visible combination of black and orange is used to indicate hazards or mark road signs. Green is the color of safety; a green traffic light means it is safe to proceed, and a green cross indicates first-aid equipment. In nature, the brightly colored plumage of male birds attracts mates.
Color is also used in the opposite way—to make objects blend with their surroundings, as in camouflage or protective coloration of animals.
Color can be used to identify objects—such as wires in telephone or television circuits—or to identify people, such as the players on a football team. Color is also important in science and industry. For example, certain colorless materials admit ultraviolet radiations; color is used to keep such radiations out where they would be injurious. Glass containers are often colored brown or dark green to protect drugs and foods from harmful rays.
Colors As SymbolsMany colors have symbolic meanings. For example, red can represent (among other things) festivity, anger, or danger. The various meanings are by no means universal; black, for example, is the color of mourning in Western countries but in parts of Asia white has that association. The vestments and hangings in some churches are colored according to the season of the church year. For example, purple, representing penance, is used during Advent.