The most important fact here is that the organism as a whole, and not just the visual system, is involved in our reactions to color. We respond in special ways to colors not only because of their physiological effects, but because of the emotions and associations they evoke.The so-called “advancing” colors— yellow, orange, and red—appear to be nearer to the observer than the “receding” colors, green, blue, and blue-green. The advancing colors suggest warmth and the receding colors coolness—but this is probably due less to the suggestion of nearness than to the association of the red end of the spectrum with fire and sun, and the blue-green end with the coolness of a forest or a body of water. Psychological studies have supported the common observation that different colors suggest different moods. Wexner (1954) found that red is usually rated as exciting, stimulating, or hostile; blue as serene, tender, peaceful; orange as distressed, upset; black as either melancholy or powerful.In view of such associations it is not surprising that our language uses various colors to express emotional states. A depressed person is “blue” and, as the song tells us, his mood is indigo. Red- haired girls are supposed to be fiery and passionate. Yellow is the mark of cowardice and green the color of envy. The explanation of these associations is often a matter of conjecture. Perhaps blue suggests depression because we tend to be dejected and lonely at night when the sky is indigo. The association of fiery hair with fiery temperament seems clear enough, though the facts do not bear it out. But what about cowardice and envy—are they yellow and green because in these emotional reactions the stomach is upset, excess yellow bile is secreted, and the natural color is drained from the cheeks?Color preferences have been investigated from time to time, but few generalizations can be made. The idea that combinations of complementaries are particularly pleasing seems to stand up; so does the idea that colors next to each other on the spectrum (red and orange, for example) are often distasteful. For most people red and blue rank above orange and yellow, and men as a whole tend to prefer red more often than blue, and the other way around for women. However, these generalizations are frequently upset by two factors: the highly individual preferences that grow out of special associations and experiences; and the “decrees” of the prevailing fashion, which exert a strong suggestive effect on our preferences, however transient they may be.People react differently under different kinds of illumination. When a person is asked to stretch his arms out in front of him, he will spread them farther apart under red light than under green light. Under red light he will also tend to overestimate time, judge weights to be heavier and lines to be longer than they actually are (Goldstein, 1942). Subjects have also been found to react more quickly than usual under red light, and slower than usual when the illumination is blue or green (Birren, 1961). These findings have been applied with some success to stimulating depressed patients and calming excited patients.Recently investigators have uncovered what is called the color-stereo effect (Kohler, 1962). Various colored patches —red, blue, orange, green, yellow—are placed side by side at random in a rectangle. If this mosaic of colors is viewed with the outer half of each eye shielded with a card, the patches will appear to be at different depths. Blue and green squares seem to float above the others; red is farthest away (contrary to the view that red is an “advancing” color). Some people with prismatic defects of the eye can obtain this effect under normal viewing conditions. The reason is that it is produced by the lens, which bends light according to wave lengths, so that hues of different wave lengths may appear to be at different distances from the viewer. Investigators have speculated that early in the development of the vertebrate eye, colors may not have been associated with hue but with subtle differences in depths of images. This color-stereo ability may explain why a small percentage of certain animals known to be color blind—cats and mice, for example—can distinguish between strong colors on visual tests.See ESTHETICS, ADVERTISING RESEARCH.