Summarize the two major theories of color vision.

The trichromatic theory suggests that the retina contains three different types of cones. Each type is maximally sensitive to a particular wavelength of light. One type responds best to short wavelengths (blue-violet), another type responds best to medium wavelengths (green), and the third type responds best to long wavelengths (red). The experience of color is a function of how a particular light stimulates the various types of cones. The opponent-process theory suggests that pairs of opposing processes are responsible for color vision. One process is stimulated by green and inhibited by red and vice versa. Another process is stimulated by blue and inhibited by yellow and vice versa. A final process is excited by white and inhibited by black and vice versa. Each theory explains different parts of vision.