WHAT GIVES YOUR EYES THEIR COLOR?
The colored part of your eye is called the iris, named for the beautiful virgin Greek goddess of the rainbow. The iris only contains transparent tissue and brown pigment, so how do eyes come in so many dazzling colors?
Eyes have different colors for the same reason the clear sky can have so many different colors, because of the complex and magical interaction between a cloudy medium and light. Light is reflected and altered by the small particles in the transparent part of the iris.
When your eyes seem to change color in different lights, it is no optical illusion; your eyes are really changing color.
Brown eyes, the most dominant iris color in the world, are simply caused by an abundance of velvety brown pigment coating the iris tissues.
Blue eyes, on the other hand, have very little pigment in the visible iris; instead, the iris is reflecting out energetic blue light rays and absorbing the less powerful darker ones. This is exactly the same optical phenomenon that makes the sky blue, called the Raleigh phenomenon. Thanks to immigration and intermarriage, blue eyes are becoming less common in the U.S. – in 1900 you were 57% of the population, but now only 17% of you have blue eyes.
Grey eyes have no pigment in the iris, like blue eyes; however, the strands of tissue in the iris are larger, and so they reflect light waves back out differently (the Mie phenomenon). On a clear day, air particles reflect back only blue, but a stormy sky is filled with raindrops, which reflect back all colors. Eyes are the same, and the result is stormy grey eyes.
Green eyes are very rare, seen mostly in people who have Celtic blood. Green comes from essentially blue eyes that have a trace amount of brown pigment mixed in.
“Hazel” is a color that is only applied to eyes, and means any combination of brown/gold/amber and green/blue/grey. Like the other eye colors, hazel eyes change color dramatically depending on the colors around them – often a hazel eye will look blue one moment and green the next.
(David Bowie had two different colored eyes due to a playground accident)
-Dr. Oliver Kuhn-Wilken
