“To use color effectively, we need to know its emotional effects, and these are readily summarized. Color is characterized by hue, brightness, and saturation. Hue is related to wavelength and hence determines whether colors are perceived as red, blue, green, and so on. Brightness refers to the intensity of light that is reflected; saturation refers to the concentration or vividness of the hue. The brighter or more saturated the color, the more pleasant it is. The most pleasant hues are blue, green, purple, red, and yellow, in that order. In terms of arousal, less bright and more saturated colors are more arousing. The most arousing hue is red, followed by orange, yellow, violet, blue, and green, with green being the least arousing. Thus, if we wanted to maximize arousal in a given room, we would probably use flocked, velvety, or otherwise textured deep red wallpaper, carpets, and curtains. [We] . . . would emphasize the more arousing hues and the more saturated colors. It is probably no accident that extremes of such a decorative scheme often prevailed in the better nineteenth-century brothels.”

—Albert Mehrabian, from Public Places and Private Spaces: The Psychology of Work, Play, and Living Environments, 1976.