Cones are sensitive to photopic higher levels of light, especially hues, or colors. When entering a light area from a dark one, we experience light adaption, but cones responding to the higher light levels recover faster than rods. The receptive photopigments in cones are called iodopsins.

Color vision is most precise at the fovea, a small area behind the iris and lens, which is what we use when we look directly at an object in medium to high light levels. The fovea consists entirely of cones, which makes it difficult to see an object in low light settings by looking directly at it.

There are believed to be three types of cones, each sensitive to a different bandwidth of light and range of colors, and each containing a different type of photopigment. Cones containing erythrolabe are sensitive to long or red wavelengths, those containing chlorolabe respond to medium or green wavelengths, and those containing cyanolabe are affected by short or blue wavelengths.

This theory of three types of cones is called trichromatic theory, which proposes that each type of cone is genetically coded for receiving and sending its specific color bandwidth to the brain.

The opponent theory proposes that the signals from the retinal cones are further converted in the brain to sets of opposing signals: red/green, blue/yellow, and black/white, which are thought to genetically define the ways in which the human brain processes color. Subjects in tests typically do not describe a color as reddish green, or bluish yellow, or darkish light, indicating that each of these combinations are processed as unique pairs of opposites, and are not perceived in the brain to describe a single color.