The colors are first of all divisible into two groups, the warm and the cold Warm colors are those in which red or yellow predominate; cold colors those in which blue predominates. The warm colors tend to impart warmth to any composition in which they are employed; they cause surfaces covered with them to appear to advance or come forward in plane; they are suggestive of impetuous or instinctive action as opposed to calculative or reflective action; they are cheerful, vivacious, joyous, and relatively stimulating and exciting. The cool colors on the other hand tend to impart coldness to any composition in which they are employed; they cause surfaces covered with them to appear to retreat in plane; they are suggestive of reflective as opposed to instinctive action; they are calm, sober and serious, and relatively tranquillizing and depressing. The hues vary in warmth and coldness directly with their purity. Vermilion is warmer than maroon or pink, and ultramarine is colder than indigo or azure.

In addition to these group characteristics each of the primary and binary hues possesses a distinctive emotional quality, which it tends to impart to its compounds and to express in any decorative composition in which it plays a part. Although these emotional qualities were understood and employed by the great colorists of the Renaissance, they have always been regarded by the layman as matters of fancy. They were, however, confirmed scientifically during the last century by Fere, Binet, Wundt and other investigators.

Yellow, the color of light and hence of life, is the most brilliant, cheerful and exultant of the colors.

Red, the color of fire and of blood, is the warmest, most vigorous and most exciting of the colors.

Blue, the color of the starlit sky and of deep and still waters, and hence of profundity and vastness and illimitable spaces, is the coldest and the most tranquil of the colors.

Used in decoration, yellow is sunny, livable and inspiriting; red is suggestive of richness, warmth, hospitality and splendor; blue of calmness, tranquillity and dignity.

Considered emotionally the three primaries, yellow, red and blue, seem not only to symbolize but also to express the cycle of human life - the exultant life of its morning, the battle and passion of its noon, the tranquillity and at last the coldness of its night. In some intuitive way man seems always to have felt this, for the three hues are constantly found together in primitive art. Certain colorists of the Renaissance reduced the feeling to a formula, and held that no scheme of color could be emotionally satisfactory unless all three of the primaries appeared in it.

The binaries are compounds emotionally as well as physically. Orange, the product of two warm colors, has the potency of both. Sharing the heat of red and the light of yellow, it is the most powerful color, being when relatively pure very decorative but hot and irritating. When greatly reduced in intensity to the golden browns and tans it is warm, cheerful and unifying.

Green and violet are products of the union of warm and cold primaries, and accordingly possess qualities markedly different from those of their constituents, as a salt differs from the powerful base and acid that combine to produce it. The greens vary widely in character, being warm or cool, sunny or somber, according to the relative quantities of yellow and blue in their composition. When partly neutralized or pleasantly broken with gray, green is calm, restful and refreshing.

Violet is the color of shadows and of mystery. Violet and purple have always had a peculiar fascination for poets, esthetes and mystics; and however fanciful their extravagances it is true that these colors do possess a subtle suggestive quality - a sense of mysteries half-explored, of fires quenched but still burning - not shared by the other hues.

Black, white and gray will be studied at some length in the chapter on light and shade. It may, however, be noted here that, used by themselves and on large areas, black can suggest only darkness and gloom, and white only a cold purity. Used together in composition, especially in small sharply-contrasted masses, they yield the same effect of concentrated activity that always results from the struggle of powerful opposites. When fused they produce neutral and characterless grays. All the grays are soft and unaggressive. True gray is as neutral emotionally as it is in color, while the tones of gray range upward toward the gentle serenity of light gray and downward toward the sobriety and melancholy of dark gray.

Black imparts solemnity to any composition in which it plays an important part. Used in small masses with other colors it serves to accent the peculiarities of the others, and thus to give an effect of concentration and vigor. White has the same power to give animation through the effect of tone contrast, and sets off the cool colors as black sets off the warm. When the cold purity of white has been banished by a little yellow, as in cream and ivory, it expresses a dignified and cheerful serenity.

The positive individual qualities of the hues vary directly with their purity. All the normal hues are powerful, bold, somewhat crude, of pronounced individuality, and obvious. They tend to lose these characteristics as they approach neutrality or are broken with gray, while at the same time they gain-in quietness, subtlety and refinement. Since interior decoration is essentially a social art, and since the social qualities demand subordination of self, it is clear that pure or almost pure colors can be used infrequently, and then in very limited areas only.

All the colors vary in emotional qualities with their luminosity, or value. Light tones, like curved lines, are associated with instinctive action, while dark tones, like straight lines, are associated with reflective action. All light tones, simply as values, and apart from any qualities of the hues themselves, have a relatively exciting and exhilarating effect, while all dark tones have a contrary effect. The high values express the ideas of activity, gayety, transience, delicacy, fragility, lightness and grace; while the low values express the ideas of inactivity, sobriety, permanence, strength, weight, repose and dignity.