The human eye detects color using three types of cone cells sensitive to red, green, and blue light.

The longer version

Cone cells in the retina come in three varieties, each loaded with a slightly different light-sensitive protein. One responds best to long wavelengths we call red, another to medium wavelengths near green, and the third to short wavelengths near blue. The brain compares the relative strength of the three signals and infers hue from that ratio.

Rods, the other major receptor type, handle dim light but carry no color information, which is why night scenes look washed out and gray. Rods outnumber cones by a wide margin, and cones cluster tightly in a small central pit. Many other mammals carry only two cone types, so their color range is narrower than ours.

Where this entry sits

These facts explore how light behaves and how human eyes turn it into the colors we see. Along the way you meet rainbows, prisms, mirrors, shadows, lasers, and optical tricks that fool our vision every day. The full list sits on the Color and Light page, where every entry is listed in order.