Cone cell
A light-sensing cell in the retina that gives colour vision in good light.
Also: cones, photoreceptor
Cones are the cells at the back of the eye that make colour vision possible. Most people have three kinds, each most sensitive to a different part of the spectrum: long, middle and short wavelengths, loosely red, green and blue. The brain compares their signals to work out colour. There are several million cones in each eye, packed most densely at the centre of vision. They need fairly bright light to work, which is why colours fade at dusk. A missing or altered cone type causes colour blindness.