People have a variety of different eye colors. Your eye color is largely determined by genetics. (Learn More)

Green eyes are the rarest color. (Learn More) Brown eyes are the most common. (Learn More) People can also have blue eyes, (Learn More)  gray eyes, (Learn More) or hazel eyes. (Learn More)

Eye color can appear to change somewhat due to pupil dilation and contrast with skin color. Though some people think eye color can change with mood, this is just a myth. (Learn More)

Studies have found some connection between eye color and certain personality traits as well as eye color and pain tolerance. (Learn More)

How Is Eye Color Determined?

Genetics are responsible for your eye color. Most of the genes that determine eye color are associated with melanin production. Melanin is a type of pigment.

Chromosome 15 has a region that plays a major role in eye color. There are two genes in this region: HERC2 and OCA2. OCA2 produces the P protein, which contributes to the maturation, storage, and production of melanin cellular structures. The lower the amount of P protein, the less melanin and the lighter the eye.

These genes result in the most common eye colors, including brown, blue, and green. Scientists still do not fully understand how certain other colors, such as hazel and gray occur.

Caucasian children are often born with blue eyes. By their 3rd birthday, their eye color can change and become darker. This happens when the melanin that causes dark eye colors is not present when the child is born. It is possible for a child to have an eye color that neither of their parents has.

Darker eye colors tend to dominate over the lighter colors. For example, if one parent has brown eyes and the other blue, there is a higher likelihood that their children will have brown eyes. However, this is not automatic.

It is also possible for genes to cause children to have two different eye colors, such as a blue left eye and a brown right eye. Referred to as heterochromia, this occurs as a result of a benign genetic disorder or faulty developmental transport.

Green Eyes

Macro shot of female greeneyes

  • About 2 percent of people throughout the world have green eyes.
  • People with green and other light-colored eyes tend to have a higher eye cancer risk, specifically intraocular melanoma.
  • When people have green eyes, they are usually not apparent until the person is at least 6 months old. Green-eyed people are typically born with blue or gray eyes that eventually transition to green.

Blue Eyes

  • Blue eyes have less melanin compared to brown, but both colors are relatively common throughout the world. In fact, everyone with blue eyes shares a common ancestor.
  • People with blue eyes tend to have greater light sensitivity.
  • Night vision is often better among people with blue eyes.
  • A genetic mutation is responsible for blue eyes.
  • People with blue eyes are more likely to have red eye in photos.

Gray Eyes

gray eyes

  • Gray eyes do not contain melanin. There are excess deposits of collagen in the eye’s stroma that essentially block blue hues by interfering with Tyndall scattering.
  • Throughout the world, only about 3 percent of people have gray eyes.
  • Depending on factors like lighting and clothing, gray eyes may appear to change color.

Brown Eyes

  • The most common eye color in the world is brown. However, the shades of brown vary greatly depending on the region where someone is born. Brown-eyed people in Europe tend to have lighter hues while people born in Asia and Africa with brown eyes tend to have darker hues.
  • About 41 percent of people in the U.S. have brown eyes.
  • Brown eyes contain a high level of melanin. The more melanin present, the deeper the color.
  • Having brown eyes may decrease your risk of environmental noise-related hearing issues.
  • Women with brown eyes may experience more pain when they are birthing babies.

Hazel Eyes

Hazel eyes are sometimes compared to brown, but they are different. The term hazel comes from the fact that this eye color looks like a hazelnut.

This color is rare. Each hazel eye is a unique color, with no two people with hazel eyes looking the same.

Eye Color & Your Mood

Happy Woman Enjoying Nature on grass meadow on top of mountain cliff with sunrise

It is a common myth that people’s eyes change color as a result of their mood. There are times when the eyes may appear to be a different color, but there are explanations for this outside of mood.

For example, eyes can look darker when someone is experiencing extreme happiness or a period of grief. This is not due to their emotions. It happens because the pupil is more dilated at these times.

When the pupil enlarges, the eyes can seem like it is darker, but this is only because the black pupil is creating this illusion. Once the pupil returns to its typical size, the darkening is no longer apparent.

Contrast is responsible for eyes appearing greener when you are angry. Anger can cause the blood vessels to dilate and become redder. This coloring can make it seem like your eyes are greener, but it is just the contrast to the redness that is causing this effect.

Eye Color & Personality

woman with dandelion

There are articles all over the internet saying that your personality traits are partially intertwined with your eye color. There is some research to suggest that this is possible, but it is not concrete.

Some research suggests the following personality traits are associated with certain eye colors:

  • Brown: vivacious, outgoing, and affable
  • Green: self-sufficient, impatient, and mysterious
  • Hazel: imaginative, adventurous, and determined
  • Gray: quiet, conforming, and self-effacing
  • Blue: sincere, smart, and sentimental

Another study looked at eye color and personality. Researchers concluded that some of the genes that play a role in eye color also play a role in frontal lobe formation. This means that certain characteristics may be associated with certain eye colors.

These results have been replicated in other studies. One found a correlation between pain tolerance and eye color. This was only a pilot study, but the results are promising for further research.

Other research looked at eye color and how it impacts attractiveness to others. The research found that if a man has blue eyes, he is more likely to seek out women with blue eyes. People with blue eyes seemed to be the most determined to find a partner who had the same eye color as them compared to those with brown and green eyes.

Eye Color & Intelligence

brain representation

Links between eye color and intelligence are far weaker. There is very limited research that shows certain eye colors may have intelligence as an associated trait.

Those who have associated intelligence with eye color have done so using research methods, such as surveys. Since these are largely subjective, there is no scientific proof that certain eye colors tend to be linked to higher levels of intelligence than others. So far, scientists agree that factors like education, home life, and environment are the primary influencers on intelligence scores.

References

The World’s Population by Eye Color Percentages. World Atlas.

Eye Color Linked to Pain Tolerance in Pilot Study at Pitt. (July 2014). Post Gazette.

Eye Color Guide – The Most Common Eye Colors. AC Lens.

Is Eye Color Determined by Genetics? (May 2015). Genetics Home Reference.

Can Your Eyes Change Color? (April 2014). The Wall Street Journal.

Does Eye Color Indicate Intelligence or Personality? What Are Your Eyes Telling the World? (November 2018). Owlcation.

Can Eye Color Predict Pain Tolerance? (July 2014). University of Pittsburgh Medical Center.

Associations Between Iris Characteristics and Personality in Adulthood. (May 2007). Biological Psychology.

3 Things That Your Eye Color Tells the World About You. (March 2018). Psychology Today.