Why is the human eye colour generally Brown, Blue and other similar variations. Why no bright green, purple, black or orange?
In: Biology
Humans do have a full rainbow of eye colors! Some colors are just very rare, and not necessarily healthy for an eye to have. Here’s what humans naturally have in increasing rarity:
Black / brown – caused by a brown chemical (melanin) at the back of the iris. Black eyes are just really dark brown.
Hazel / amber / yellow – caused by a yellow chemical (lipochrome) and melanin at the back of the iris
Blue – very little if any pigments in the eye. There is a clear squishy layer that reflects blue better than other colors (Tyndall scattering). The thickness of this layer can affect the brightness of the blue. Most irises would have this blueness if there is no melanin. Newborn babies sometimes start with blue eyes before they become pigmented.
Green – amber pigmentation, but not much. The blueness of the iris also shows through. The colors mix and make green.
Grey – no pigmentation like blue eyes, but the clear squishy layer is too thin to reflect much blue light. The iris’ opaque whitish color shows (kinda like the color of the whites of your eyes). Another variation is there is something goopy (collagen) that absorbs a little bit of every color. We’re still trying to figure out this one.
Red – blue or grey eyes where there is little to no coloration, and the red blood vessels show through. This is usually not healthy.
Purple / violet – red eyes that still have a little blue coloration left. Elizabeth Taylor famously had this eye color.
Why no neon colors? – human bodies simply don’t have a lot of pigments to put into our eyes. It’s kinda like mixing paint, and we only have brown and yellow. Our bodies sometimes do tricks with blue and grey, kinda like putting paint on white paper with harsh lighting to make another color sort of appear. For some, like neon green, you can’t get that color without a neon green paint. Just biology there.
Latest Answers