All the Colors We Cannot See

Tetrachromacy in Humans

Two to three million colors, that is the approximate number the typical human eye can see. This is due primarily to the fact that our eyes contain three different types of photoreceptors, known as cones, that are responsible for detecting wavelengths in the visible spectrum, with different yet overlapping ranges. They are known as short (S), middle (M) and long-wave (L) cones, because each…