Your eye color results from the amount of melanin your body makes. Melanin is a pigment that gives color to your eyes, hair and skin. Genes determine your eye color. The iris (the colored part of the eye) can range from light blue or gray to very dark brown, in a full spectrum of shades. No two people have the exact same color eyes.
Eye color refers to the color of your iris. The iris is the colored part of the eye that surrounds the pupil. Your pupil is the small black opening in the center.
The iris has two layers. Eye color results from the amount of pigment (melanin) you have in the front layer (stroma). Almost everyone (even people with blue or green eyes) has brown pigment in the back layer of the iris.
Your eye color is like your fingerprint. Nobody else in the world has the exact same eye color as you do. The amount of melanin you have in your iris is totally unique to you.
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Eye colors vary based on how much melanin your body makes. Melanin is a naturally occurring pigment that gives color to skin, hair and eyes.
Skin cells called melanocytes are responsible for making melanin. Everyone’s melanocytes produce different amounts of pigment. People whose skin cells don’t make much melanin have lighter eyes. People whose skin cells produce more melanin have darker eyes.
Scientists used to think only one gene determined eye color. They thought that a simple inheritance pattern caused someone to have more or less melanin. For example, they thought two blue-eyed parents wouldn’t be able to have a child with brown eyes.
Today, scientists know that the inheritance pattern is more complex. Many genes work together to determine what color eyes you have. Your eye color depends on the color of your parents’ eyes and the eye color of your relatives. Sometimes, genetic mutations (changes) cause someone to have different colored eyes than anyone else in their family.
About 10,000 years ago, everyone in the world had brown eyes. Scientists believe that the first blue-eyed person had a genetic mutation that caused the body to produce less melanin. Today, about half of the people in the United States have brown eyes.
Eye colors range from very light blue to dark brown. Some eyes also have flecks or spots of darker or lighter colors mixed in. Eye colors can be many different shades of:
People with blue eyes don’t actually have blue-colored pigment. The iris only looks blue because of the way light reflects.
An eye with less melanin absorbs less light. Collagen fibers in the eye scatter the light, and it reflects off of the surroundings, making eyes appear blue. People with lighter eyes may be more sensitive to light because they have less pigment to protect their eyes from bright light.
Many babies are born with blue or brown eyes. But newborns can have any eye color. As a baby grows, melanin continues to develop. If a blue-eyed newborn develops more melanin in their irises, their eyes might darken or turn brown or hazel.
This change usually happens in the baby’s first year. But it can take up to a few years for eyes to turn the color they’ll be for the rest of their life.
Eye colors usually stay the same throughout a person’s lifetime. Certain health conditions and disorders can cause changes in eye color.
Your eye color might appear to change a bit from time to time. For example, your eyes might look like they’re a darker shade of blue if you’re wearing a blue shirt. The change in colors happens when light reflects off of objects around you.
Some people have a ring of darker pigment around the outside of their iris. Providers call this a limbal ring. It can fade and become less noticeable with age.
A condition called heterochromia causes the iris to be different colors. People with this condition may have different colors within one eye (for example, the iris may be half one color and half another). Or they may have a different color in each eye.
Most often, heterochromia results from a harmless gene change. It usually happens sporadically, which means there aren’t any other symptoms or health problems that happen with it. Rarely, heterochromia can result from an injury or disease, such as a tumor in the eye. A condition called Horner’s syndrome can also lead to heterochromia.
Several conditions can affect eye color. These include:
A type of medication called prostaglandins can cause the iris to change color. Providers use prostaglandins to treat glaucoma. Prostaglandin is also the main ingredient in a serum called Latisse® that lengthens eyelashes. These medications can cause the eyes to become darker.
Providers have found a connection between the color of your eyes and your risk of developing certain eye conditions. People with brown eyes are less likely to have macular degeneration, cancer of the eye or diabetes-related retinopathy. Providers believe this is because brown pigment may offer the eyes more protection, lowering the risk of these diseases. But people with brown eyes have a higher risk of getting cataracts.
A note from Cleveland Clinic
Your eye color is unique to you. No two people in the world have the same color eyes. Eye colors range from light blue to dark brown and every shade in between. Some people have flecks or stripes of various colors or a darker ring of pigment around the iris. Genes from your parents, grandparents and other relatives determine what color your irises will be. These genes also play a role in the color of your hair and skin.
Last reviewed by a Cleveland Clinic medical professional on 06/10/2021.
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