The deactivated OCA2 gene responsible for “blue” eyes removes most of the brown melanin pigment and reduces the size of the remaining melanin particles to a maximum of 1/400,000,000 of an inch.

This reduction creates Tyndall scattering. The shorter blue light rays are reflected back to the observer by the remaining microscopic melanin particles.

There are NO pigmented blue eyes. All blue irises are created by unabsorbed reflected blue light.

Blue jays, bluebirds, blue butterflies, blue dragonflies, as well as blue eyes, are all free of any blue pigment.

If you beat on a blue jay feather with a hammer, the feather will turn black when the surface optical effect is destroyed.

There’s also no such thing as a white bird feather.

In birds, “white” and “blue” are schemochromes, optically produced colors from the coherent scattering of light, the same interference pattern that causes “color” in an oil slick.

A parallel phenomenon, Rayleigh scattering, the selective scattering of light, makes the sky and the ocean appear blue.

Green eyes are caused by an increase in the size and quantity of melanin particles, just as waterborne micro-organisms (phytoplankton, etc.) change a blue ocean to green.

Light brown and dark brown eyes are caused by a still further increase in the size and quantity of melanin particles.

However, alien black, brown, orange, and/or yellow pigmentation in an iris does indicate toxic phenotypic (not genotypic) disorders, but normal brown irises are actually “sunglasses” for the eyes.

The idea that brown eyes are toxic appeared because iris diagnosis was originally developed by German racial hygienists.

Blue eyes, blond hair, and fair skin were conjectured defining features of the so-called Master Race, also known as the Nordic Race, Aryan Race, Nordic-Aryan Race, and Nordic-Atlantean Race.

On planet Earth, diffractional “structural” blue is more common than pigmentary blue.

Patricia Sloane (The Visual Nature of Color, 1989) wrote …

“The Tyndall blues, explained in terms of diffraction, account for many of the blue colors seen in beetles, butterflies, birds, and mammals. Named after the Irish physicist John Tyndall, who discussed the phenomenon in 1869, they provide another example of the ubiquitous visual affinity between blue and black. The Tyndall blues might as appropriately have been called the Tyndall blacks. They are typically created when a layer of melanin, a black pigment, is overlaid by translucent ridges, scales, or other structures that scatter light. A blue wing feather from a blue jay, for example, contains no blue pigment. When crushed, the feather is reduced to a black, not blue, powder.”