COLOR covers everything, outlining and emphasizing shapes and making them easy to see. Its wide distribution, instant appeal, and powerful emotional effect made it a dominant element in the language of decoration. Delight in color is a universal human characteristic, found among the most primitive as well as among the most highly cultivated peoples. It has been a factor of importance in both biological and social evolution, and is doubtless destined to be an even more important factor in the cultural evolution of the future. Having the power to arouse or to sooth, to cheer or to depress, color largely creates the atmosphere, the in-dwelling and pervading influence, of our homes. By color our rooms are made grave or gay, warm or cool, suave, sympathetic or repellent.

Color is a property of light. When the light goes out color goes with it. Sitting in a drawing room as afternoon passes into evening, we see the rich and glowing colors of textiles, pictures and porcelains lose first their brilliancy, then their distinctive hues, and finally disappear altogether, as a flaming sunset fades into gray and deadens into black.

Solar energy reaches the earth in the form of ether vibrations of varying wave-length. Those which fall between certain maximum and minimum limits affect the nerves of the eye and yield the sensations of color. The white light of the sun is made up of a great number of rays so blended as to yield no sensation of color. If, however, a beam of white light be passed through a prism it is broken down into its constituent elements, which appear as separate bands of colored light. Some surfaces, illumined by white light, reflect practically all the rays, and therefore appear to be white. Other surfaces absorb practically all the rays and reflect none, and therefore appear to be black. Most surfaces, however, absorb all the rays except those which yield a single color sensation, and therefore appear to be of that color. Thus a blue ribbon is a ribbon which absorbs all the rays except blue. Most surfaces, moreover, reflect not only a characteristic colored light but also a greater or less amount of white light, so that a blue ribbon may be so light as to appear almost white, or so dark as to appear almost black.

The light rays, as they are reflected by all the surfaces within the field of vision, are received by the eye and focused upon the retina, a recording apparatus of incomprehensible fineness and complexity, made up of millions of nerves which appear under the microscope in the form of infinitesimal rods and cones, each of which is connected with the optic nerve leading to the brain. Just what takes place in the eye when light enters it is not known, but there is reason to believe that while the rods are chiefly sensitive to white light the cones are sensitive to vibrations of definite wave-lengths only, and are thus capable of communicating to the brain a definite color sensation. When the cones normally affected by vibrations of a given wave-length are absent or fail to function properly the corresponding color sensation cannot be registered in the brain, and the person whose eye is so constructed is color blind. The color nerves tire quickly. When the eye is compelled to gaze at the same hue for some time the nerves employed become tired and incapable of a vivid sensation, as every one has noticed in matching colors. They must be relieved temporarily by another set of nerves - a fact that shows the physical basis for the esthetic need of variety in color composition.

The study of color is made more difficult by the fact color phenomena are investigated and described in terms of colored light by the physicist, and in terms of pigments by the artist and color worker. The scientist, passing a ray of light through a spectroscope, finds that it is broken down into a flat band of color containing more than a thousand hues, with red at one end and violet at the other; that these hues stand in definite relationships to each other; and that they behave in certain ways when variously combined.

The artist, however, does not work with colored lights, but with pigments, which lack the power of complete absorption and therefore yield results different from those obtained when working with light. Since we are concerned in interior decoration almost exclusively with the pigment colors, and are in fact concerned primarily with color perception and only incidentally with color theory, it seems wiser in the brief study of color to be included in this volume to follow - with reservations - Chevreul and the older colorists. This method will afford the easiest and most simple approach to the subject, and the most helpful results in practice. The student who wants an accurate knowledge of the scientific theories of color can consult Rood, Von Bezold and Luckiesh.

There are three pigmental hues which cannot be produced by any admixture of other colors, but which are themselves capable of producing, in conjunction with black and white, all other colors. These three colors, which for this reason are called the primaries, are red, yellow and blue. Being as unlike as possible, they may, for the sake of clearness in color study, be conceived as lying at the points of an equilateral triangle inscribed within the circumference of a circle, as in Figure 7. Any two of the primaries can be mixed to form a third color which partakes equally of the qualities of its constituent primaries. Thus red and yellow yield orange, yellow and blue yield green, and blue and red yield violet. These resultant hues, which are called the secondaries, or binaries, will accordingly lie midway between the two primaries which unite to form them and directly opposite the third primary on the chromatic circle.

Figure 7. - The three primaries, red, yellow and blue, and the binaries, orange, green and violet; the chromatic circle, showing a sequence of twelve hues.