How do eyes see color?
Eyes see color using cells called cones in the retina. Most people have three types of cones, sensitive to red, green and blue light, and the brain combines their signals.
Light enters the eye through the cornea and lens and lands on the retina at the back. The retina has two main kinds of light-sensing cells. Rods work in dim light but do not detect color, which is why the world looks gray at night. Cones need brighter light and handle color and fine detail.
Each type of cone responds most strongly to short, medium or long wavelengths of light, roughly matching blue, green and red. The brain compares how strongly each type is stimulated. Yellow light, for example, excites both red and green cones. By mixing these signals, the brain can tell apart roughly a million different shades.
Color blindness
When one type of cone is missing or works differently, people have trouble telling some colors apart. Red-green color blindness is the most common type. It affects about 1 in 12 men and 1 in 200 women of Northern European descent, because the genes involved sit on the X chromosome.
Did You Know?
Some animals see colors we cannot. Many birds and insects see ultraviolet light, and mantis shrimp have up to 16 types of light-sensing cells.
This answer is general information, not medical advice. For a personal health question, talk to a doctor.