Color is more a perceptual effect han a physical one. Our eyes perceive light in certain ranges of wavelengths as having color red, green, or blue, and then mixtures of these may be perceived as a different color entirely (for example, white). Having studied the spectrum of light, we are in a good position to understand this potentially confusing subject.

Applications

A close up view of a computer screen

Color photography and color displays for television and computers owe their existence to the fact that we can make almost all colors by mixing red, blue, and green light.

Objects are perceived to have a color because they reflect only part of the spectrum of the light with which they are being illuminated. The result depends somewhat on the illuminating spectrum (consider what happens if the illuminating light only contains a particular red wavelength, and the object reflects other reds well but not this one), and it can happen that certain objects will appear to be the same color when viewed with one kind of light, but of differing colors when viewed with another. Physics provides a description of the basis for the sensation of color that explains puzzles such as this one.

A rainbow at sunset

A normal rainbow