....and brought them unto Adam to see what he would call them... Genesis 2:19
"Human eyes come in a range of colors. Although we typically think only
brown, blue, green, and hazel, the eyes can be even more colors,
including gray and amber. In very rare cases, eyes can appear red or
violet. Individuals with these colors typically produce extremely low
amounts of pigment, if any. The red color is from blood.
As with skin and hair, there are the same two color pigments: eumelanin
and pheomelanin. However, there are at least 16 different genes that are
known to contribute to eye color. The color will also appear different
depending on whether the pigment is on the front layer of the iris or
the back layer of the iris.
Lipochrome is a yellow compound that results from breakdown products
from lipids. This molecule contributes to the green and amber eye
colors. Light scattering through the layers of the iris leads to the
appearance of the blue color as well as green and gray. Individuals with
gray eyes have additional collagen fibrils in the iris that make the
eye appear gray.
Mutations and polymorphisms in OCA2, a gene involved in melanin
production in the eye, have been linked to reduced melanin presence in
the front layer of the iris. Such changes result in eye colors other
than brown.
Interestingly, individuals with blue eyes do not have
mutations in OCA2. Instead, they have a mutation in HERC2, which is
adjacent to OCA.
Scientists believe the evidence suggests that most
people with blue eyes all descended from the same individual with a
mutation that knocked out Herc2 and OCA2 simultaneously.
