The color of a body depends on its nature, and the light in which it is viewed. A scheme of color that is harmonious by daylight may be just the opposite at night when viewed by artificial light. Different bodies or substances, like dyestuffs, etc., owe their property of color to the light that falls on them, and not to the body or substance itself. This fact may be illustrated by allowing different colored lights to fall on the same substance, and noticing the colors thus produced.
Sunlight, as any other light, comes to us in the form of waves vibrating at different rates. Each wave is one color, and when they are mixed in a beam they produce white light. Light may be separated into different colors or wave lengths, by means of a triangular prism of glass, whereby the rays are refracted and those with the greater vibra-
Fig. 65. - Spectrum.
tion are bent more. In this way sunlight is separated into its component parts. The colors thus obtained make up what is called the spectrum (Fig. 65). The spectrum contains red, orange, yellow, green, blue, indigo, and violet rays. These rays are not all of the numerous components of white light, but only the principal or primary ones.
Light in a dry goods store, where fabrics are displayed, should be diffused daylight, while in a ballroom a softer light, rich in yellow and orange tints, is preferable. Every opaque object assumes and reflects a color. A piece of red cloth looks red because it selects from white light mainly red for reflection.