I keep hearing that other color eyes have pigment to make them that color but with blue eyes they have no pigment and it is the physical structure that only reflects blue.
How is that any different than any other color?
Doesn’t red paint only look red because it reflects red light?
Doesn’t brown pigment only look brown because it reflects brown light?
I thought that is how all color worked, by reflecting only that kind of light.
People say it about blue eyes like it’s somehow different but it sounds the same to me
In: 7
While I can’t speak to the truthfulness of this claim, I can do the physics. Pigments get their color from chemistry – the way that light interacts with molecules.
There is another way to create color. Well, a few but, we can skip the rest. This one comes from the physical structure of the object. For instance, the shiny rainbow oil slicks that can develop on the wet ground. This happens because of the wavelike nature of light – when the surface shapes are around the same size as the wavelength they can interact differently with different wavelengths. Reflecting some and absorbing others.
We have no pigment, and the underlying colour of the iris reflects blue. Green eyes are caused by a yellow pigment I forget the name of. The yellow pigment and the blue base gives green. The other colors are caused by a mixture of brown by melatonin, this yellow one I forget the name of, and the blue of the iris.
The difference is how the colors are separated.
With pigments, some of the colors are absorbed and some are reflected. The reflected ones are what we see.
But certain materials or surfaces simply reflect different colors differently. So if the other colors get yeeted somewhere else and only blue makes it to your eyes, then you see blue.
It’s why the sun is yellow and the sky is blue. The sun is yellow because the blue got yeeted somewhere else by the atoms in the air. The sky is blue because it’s the “somewhere else”. https://www.youtube.com/watch?v=_Yli-yvNy-k
Blues eyes are blue by the same principle. The other colors mostly pass through (and are absorbed somewhere passed the iris) and blue gets yeeted back toward the outside world.
A lot of “blue” you see in living things in nature is something called “structural color”, where the color is the product of scattering of light, or very specific ways of reflecting light, but is not the result of a blue pigment that is blue and absorbs other light.
You see this often on butterflies, and these make a good example for what’s coming next.
A lot of color you see elsewhere is due to pigment. That is you can take a yellow/red/green/etc thing, grind it down, and then have a yellow/red/green powder/paste.
With structural color you can’t do this. Take the blue bits from a butterfly and grind them down and you won’t get a blue powder, because the blue you’re seeing is due to complex behaviors of light when it strikes a very specific layering of optical properties in the butterfly wings. Take away the precise layering and you don’t get the color anymore. There’s no blue dye in there, it’s all optical trickery.
Be Smart on YouTube has a good video on how there’s technically no blue in nature.
Blue Eyes do have pigment. If you have no pigment in your iris at all, you’ll have red eyes (like albinos do).
But people with blue eyes have less pigment.
The blue itself comes because of complicated physics: blue light has the highest frequency wavelength; this means it wiggles about a lot more than other colours do and thus has a larger change of hitting a molecule and being reflected away (absorbed). The same reason the sky is blue.
All colour DOES weork that way; absorbing some wavelengths of light and reflecting others.
What they are saying is that all eyes are naturally blue BUT some people have an additional pigment in their eyes which changes their colour (brown, green, whatever).
People without the additional pigment have blue eyes. This pigment, though, dominates over the eye’s “natural” colour and makes them appear the other ones.
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