What is eye color and how is it determined? There are many factors that go into the color of your eyes. There are a lot of things people say about eye color, how much of it is true?
First, you need to understand what eye color is. The colored part of your eye is a combination of two muscles making up the Iris. It has one muscle that acts as a sphincter to make the black part (pupil) smaller. The other muscle pulls open the pupil to dilate your eyes. This muscle is naturally pink in color which brings us to our first color. People with a condition called Albinism are deficient a colored pigment called melanin and will have pink eyes. Melanin is created by melanocyte cells all though your body, most notably in your skin and eyes. The more melanin you have, the darker your skin and eye color. If you have a light amount of melanin, then your eyes are blue, the next color is green, and finally brown. All the other colors, like hazel, are colors that run between blue, green, and brown.
The main factor in that determines your eye color is your genetics. There are at least eight genes that determine your eye color, which explains how there can be such a difference between people. The different genes generally control how much melanin and other pigments are produced in the iris. The more pigment that is present, the darker the eye color is from blue to brown. Blue eyes have very little pigment in the iris and pigment absorbs light. Without this absorption, a natural scattering of light happens called Tyndall scattering creating blue colors. This phenomenon is very similar to Rayleigh scattering that makes the sky blue.
Another influencer of eye color is what type of light is hitting the eyes. Generally, this is the case if you have lighter eyes. If you have blue eyes, and you wear a blue shirt, your eyes will naturally seem bluer in color. Sunlight will bring out different colors of the eye versus indoor lighting. Sometimes people will report that their eyes seem to change color depending on their mood. Mood is not an influencer of eye color, but the size of your pupils can change with your mood. If your pupil dilates, then the iris muscle is pushed together concentrating the amount of pigment, this can darken your iris some. When you are in bright light, your pupil gets smaller which spreads out the pigment in the eye and it can lighten your eyes.
There is a wide variety of eye color in European descendants, but with much of the world the dominant color is brown. Brown is the most common eye color worldwide at around 79%. The rarest eye color is Green at around 2% of people. Green eyes are most common in people with Northern Europe descent. Also, green is usually listed as the most attractive eye color when surveyed. Your eyes do tend to darken as you get older since melanocytes will continue to make melanin. Some eyes lighten with time if the pigment starts to fall off the iris, which can cause Pigmentary dispersion syndrome and glaucoma. For the most part, the color you have now, is the color you will always have.