Or there may be a completely different explanation. It could be that different people have gray eyes for different reasons and so all of the ideas are right. We don't know which of these ideas about gray eyes is right. As you decrease the amount of melanin present the blue eyes look lighter and lighter until they look colorless or light gray. A little melanin in the front of the eye gives you blue eyes. You can imagine the difference between blue and light gray eyes like a dimmer on a light switch. Even less here than is found in blue eyes! Blue and gray eyes are very similar genetically. One idea is that in light gray eyes, there is very little melanin on the front of the iris. The blue reflection of light is clouded over by the dark layer in front causing a dark gray color. One theory is that dark gray eyes come from a thin layer of melanin on the front layer of the iris. This means we can't even guess at the genes that might be involved.Īnother idea about gray eyes has to do with the amount and location of melanin. Undoubtedly there are genes that determine this we just don't know anything about them. We do not know genetically how the amount of collagen in the stroma is determined. You could imagine that the amount or size of the proteins in the stroma could determine how gray the eyes appear. Remember that the blue eye color is caused by light reflecting off of the protein collagen in the stroma. So we have one guess about why eyes look gray. This kind of scattering is called Mie scattering. When the light hits the water drops, it looks gray or white because the larger particles scatter all of the wavelengths of light equally. It looks gray right? That is because the light from the sun is reflecting on large drops of water. Some eyes are blue for the same reason the sky is blue. This effect is called Rayleigh scattering. This is because light from the sun hits particles in the atmosphere and reflects blue. The sky is dark in space but when we look at it from Earth during the day, it looks blue not black. When the light hits the collagen it bends and looks blue. The collagen in the stroma gets in the way of the light on its way back to the front of the eye. But the light doesn't reflect back through a completely empty stroma. In blue eyes, though, light can pass right through the clear front of the iris and reflect off the melanin in the back of the eye. So brown eyes are dark because lots of melanin in the front layer absorbs any light hitting the iris. The difference is that brown eyes also have a lot of melanin in the front layer and blue eyes do not. Most differences in eye color come from the amount of melanin made on the front layer.įor example, both brown and blue eyes have lots of melanin in the back layer. We will get back to that later.Īlmost all eye colors have a lot of melanin on the back layer of the iris. One of these proteins is called collagen. The stroma is a clear tissue with many proteins floating around in it. In between the two layers is an area called the stroma. There are two different layers in the iris, a front and a back one. How can this one color pigment be responsible for many colors including blue, brown, and gray? It has to do with HOW MUCH and WHERE the melanin is made in the eye. This might seem weird at first since melanin is dark brown or black. Different amounts of pigment in the iris lead to different eye colors.
#SILVER BLUE EYES SKIN#
The major pigment in the eye is the same as the one in skin and hair - melanin. And why some eyes are brown while others are blue.
It is why some flowers are red and others are blue. Pigments are what give nature all of her colors. The color comes from dye-like molecules called pigments. When people talk about eye color, they are talking about the color of the part of the eye called the iris. But as you will read later on they are not exactly the same.Īlthough we do not know the exact genes that cause gray vs. blue eyes, we do know a lot about what makes different eye colors.
This is probably because it is likely that the genetics of the two are very similar.
Not many scientists have studied the differences between blue and gray eyes. But mostly about blue, green and brown eyes. Scientists know a lot about the genetics of eye color.
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