In order to perceive color and pattern, living organisms must be able to see. Our human eyes contain highly sensitive “rod” cells that respond to the amount of light entering the eye, from white to black. The companion “cone” cells respond to colors but require high levels of light in order to act. Most fish see quite well, with eyes similar in structure and sensitivity to our own, though their focal range and mechanics differ somewhat.
Most fish perceive the colors blue and yellow; a few also respond to red and green. But fish may have visual abilities that we lack. Some species can sense light in the ultraviolet (UV) range; a few are sensitive to certain types of polarized light. What we might see as a bright splash of a specific color, for example, a fish might perceive as just part of the background. Alternatively, a fish might “see” higher contrasts (for example, two visual perceptions from the color yellow: visual yellow and UV yellow).