The color of your eyes comes from pigmentation in the iris, a muscle tissue that controls the size of your pupil and lets light inside your eye. Inside the iris there is a brown pigment called melanin that gives your eyes their color. The amount of melanin and how it is distributed determines your color tone. Brown is the most common eye color in the world.

Even people with blue or green eyes have some melanin in their eyes. They simply have much less melanin than people with brown eyes. The iris consists of two layers, and people with light eyes have melanin in the invisible posterior layer. People with brown eyes have melanin in both layers of the iris.

Eye color pedigree

Eye colors can range from pale blue to dark brown that looks black.

Brown is the most common eye color in the United States and the world. More than half of people have brown eyes. Green eyes are the rarest, and only 2% of people have these eyes

Eye colors in the United States fall into the following categories:

• Brown eyes: 45%
• Blue eyes: 27%
• Hazel eyes: 18%
• Green eyes: 9%
• Other eye colors: 1%

People with albinism may not have any pigment in their eyes, so their eyes may be red or pink. This happens because the iris is clear without melanin and allows blood vessels to emerge through them

It is very rare to have two different eye colors. Aniridia is a rare condition in which a person loses part of the iris in one or both eyes.

Genetics of eye color

• Multiple genes help determine your eye color. Research shows that you can’t predict a child’s eye color based on parental eye colors just because many genes are involved.
• Genes affect how melanin is made, transported, and stored in your body. For example, a protein encoded by a gene can affect the amount of pigment produced by melanosomes (cells that make melanin). If you have a little pigment, you will end up with blue or green eyes

Genes involved in determining your eye color include:

• OCA2
• HERC2
• ASIP
• IRF4
• SLC24A4
• SLC24A5
• SLC45A2
• TPCN2
• TYR
• TYRP1

Why brown is more common

• Researchers believe that brown eyes are most common because our ancestors and the first humans had this eye color. There is an advantage to having brown eyes in areas with a lot of sunlight because melanin protects the eyes.
• Ancestors who came from Africa had brown eyes to protect them from harmful UV rays

Other causes of eye colors

• Blue and other eye colors are developed from a mutation (genetic change). One ancestor likely had a mutation 6000,10000 to <>,<> years ago that affected melanin production and resulted in lighter-colored eyes.
• Researchers believe that light eyes appeared as soon as our ancestors left Africa and spread to Europe. These areas had less sunlight, which meant there was less advantage than having more melanin
• The reason why a person’s eyes appear green or blue has to do with the amount of melanin in the iris. When there is less pigment, there is less light that can be absorbed. Light is dispersed and reflected. The eyes with the least amount of melanin are blue. Eyes with more pigment will be green 

Why does a child’s eye color change and when to adjust it permanently

• Many babies are born with blue eyes, but they change over time. It increases the melanin in their eyes and can brown or make them darker within 12 months. It takes time for pigment to grow in children
• By the time a child reaches the age of three, eye color is usually permanently adjusted.2 This happens faster for most babies, and their eyes are adjusted at nine months. An adult’s eye color can change due to: 

genetics

• shock
• disease
• Sun rays damage
• Medications
• Impact on eye health

People who have certain eye colors are more likely to have different health conditions.

There are advantages to brown eyes, such as low risk: 

• Macular degeneration
• Diabetic retinopathy
• Eye cancer
• If you are concerned about your eye color or the general health of your eyes, talk to your eye doctor and have an eye exam.