Green has traditionally been called therarest eye color. But new classifications say another color may be even less common—gray.
Eye color is an inherited trait with multiple genes affecting the shade. Genes related to the production of pigments—melanin, eumelanin, and pheomelanin—dictate the color of your skin, hair, and eyes. A person's eye color reflects a unique combination and concentration of pigments in the iris.
This article looks at rare eye colors and the genetics of different eye colors. It also discusses conditions that may change your eyes' appearance, health associations of different colors, age-related changes, and how to change your eye color.
The Anatomy of the Iris
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Most Common and Rarest Eye Colors
The conventional eye colors have generally been thought of as:
- Brown
- Blue
- Hazel (sometimes grouped with amber)
- Green
Of those four, green is the rarest. It shows up in about 9% of Americans but only 2% of the world's population. Hazel/amber is the next rarest of these.
Blue is the second most common and brown tops the list with 45% of the U.S. population and possibly almost 80% worldwide.
Black is not an eye color. While some eyes may look black, they're either just a very dark brown or have large pupils (more on this below).
Gray: The Rarest Eye Color
New classifications have determined that gray is its own standard color. (It was previously, and incorrectly, lumped in with blue.) With this change, gray now tops the list as the rarest eye color.
| EYE COLOR | U.S. POPULATION | WORLD POPULATION |
|---|---|---|
| Gray and other | Less than 1% | Less than 1% |
| Green | 9% | 2% |
| Hazel/amber | 18% | 10% |
| Blue | 27% | 8% to 10% |
| Brown | 45% | 55% to 79% |
There's not much information on gray-colored eyes. In studies, gray and blue have historically been combined.
This may change since the American Academy of Ophthalmology (AAO) has separated gray into an "other" category, which it shares with rare eye color differences discussed later in this article.
What Determines Eye Color?
Eye color is influenced by the production of melanin, or pigments, in the iris—the colored part of your eye. More melanin means darker eyes, less means lighter eyes.
Different types of melanin determine the specific hue of eyes. Eumelanin is a black-brown pigment responsible for darker eyes, hair, and skin. Pheomelanin is a yellow-red pigment that behind green or amber eyes, red hair, and freckles.
People in countriesfarther away from the equator tendto have lighter-colored eyes and skin. Darker eyes and skin are common in warmer locales, closer to the equator. Of course, all of this comes down to genetics.
Genetics of Eye Color
Scientists used to think that eye color inheritance was a simple matter of whether genes present were dominant (expressed whenever present) or recessive (only expressed when matched with the same gene).
In other words, brown eye color (considered dominant) would be expected in a child even if only one parent has brown eyes. Blue eye color (considered recessive) would only be expected in a child with two blue-eye parents.
But recent discoveries have shown that the genetics of eye color are more complex than that. Two people with brown eyes, for example, can have a child with lighter eyes.
Most eye-color genes have something to do with the transport, production, and storage of melanin. More melanin in the iris makes for brown eyes, while less of it may mean blue, hazel, green, or gray eyes.
The amount of melanin present in the front of the iris, the back of the iris, and in the stroma layer between them matters too.
What Genes Determine Your Eye Color?
Multiple genes influence the various combinations and concentrations of melanin. The OCA2 gene plays the most prominent role in determining your eye color.
Researchers have identified at least nine other genes involved in the production and distribution of pigments. For example, the HERC2 gene turns the OAC2 gene on and off as needed.
Other genes that play a role in eye color include ASIP,IRF4, SLC24A4, SLC24A5, SLC45A2,TPCN2, TYR, andTYRP1. Countless combinations of these genes produce a continuum of eye colors in individuals.
Eye Color Genetics
Other Eye Color Differences
Abnormal eye colors or appearances are rare and fall into the "other" category with gray eyes.
Heterochromia
People with heterochromia have different colored eyes. Some people are born like this. Often there's no known reason for it, but it can be caused by a condition known as piebaldism, a lack of pigment-producing cells in patches of hair, skin, and, in some cases, one eye.
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You can alsodevelopheterochromia later in life. It can occur due to:
- Injury
- Eye surgery
- Medication, including some glaucoma drugs
- Illness, including glaucoma and diabetes
Heterochromia itself doesn't need to be treated. If it's caused by an underlying condition, though, you should get proper treatment for that condition.
The Science Behind Different Colored Eyes
Anisocoria
Anisocoria is when someone has two different pupil sizes. The larger the pupil, the more black there is in the center of the eye. This isn't an eye color, but it can make someone look like they have heterochromia.
Anisocoria is usually harmless, but it can be a symptom of some serious eye problems. These may include:
- Nervous system problems
- Previous eye damage
- High stroke risk
- Viral infection
- A condition called Adie's tonic pupil, in which one pupil doesn't react well to light
- Horner syndrome, a rare condition involving drooping eyelids, different-sized pupils, and lack of facial sweat
If you have anisocoria along with certain other symptoms, you should see an eye doctor. Watch for symptoms such as:
- Dropping eyelids
- Difficulty moving your eye
- Pain in your eye
- Fever
- Headache
- Reduced sweating
Anisocoria itself doesn't need to be treated, but an underlying condition may need to be.
Albino Eyes: Red, Pink, Violet
Albinism is low amounts of melanin in the skin, hair, and eyes. In some people, it only affects the eyes. This is called ocular albinism.
People with albinism may have lighter versions of standard eye colors. But they may also have eyes that appear:
- Red
- Pink
- Violet
The iris doesn't actually have red, pink, or violet pigment, though. These colors result from blood vessels at the back of the eye being visible. In other people, the color of the iris blocks the view of these blood vessels.
People with albinism often have serious vision problems. That's because melanin helps the eye develop normally before birth.
Eye Color and Your Health
Having a rare eye color or appearance may seem special and distinctive. It may go beyond appearance, though, as eye color (or shade) may be tied to certain health benefits or concerns.
A2014study concluded women with light-colored eyes were better able to withstand pain during pregnancy than those with darker eyes. The sample size for this study was relatively small, including just 58 women, but another small study had similar results.
A review from2015suggests people with darker eyes may have a reduced risk of hearing loss not related to age.
However, research from2011, suggests a link between blue eyes and type 1 diabetes. This work hasn't been replicated, though.
Lighter eye color is also associated with an increased risk of macular degeneration, which causes a loss of your center field of vision, as well as ocular melanoma (cancer in or around the eye).
This is all preliminary work, though. More research is needed to confirm such connections and associations.
Eye Color and Changes With Age
Your eye color can change in adulthood and may take on a more rare appearance. Sometimes, it's not a cause for concern. Other times, it's due to diseases, medication use, or injury and may need treatment.
If you don't have gray eyes but they appear to become more gray over time, it may be due to a cataract. This is a clouding of the eye's lens. Cataracts can affect your vision and may need to be surgically removed. Let your eye-care provider know if your eyes appear to be turning gray or milky.
Brown freckles can develop in your iris over time, usually due to sun exposure. Most of them are harmless but sometimes they can be cancerous, so bring those to your provider's attention if they occur.
Conditions like Fuchs heterochromic iridocycl*tis can lighten your eye color and may lead to serious vision problems. Fuchs involves inflammation in some of the structures at the front of your eye. It may cause:
- Loss of pigment in your eye, which changes the color
- Atrophy (wasting) of the iris
- Cataracts
- Glaucoma, which can cause loss of vision
It may seem fun or exciting to have your eyes change color. Because of the potential for serious vision problems, though, you should be evaluated by a healthcare provider.
Changing Your Eye Color
If you want to change your eye colored contact lenses are the easiest option. You can have color added to lenses you wear to correct your vision.
If you don't need corrective lenses, you can order some that are purely for looks. However, you should still see an eye-care professional and get a prescription for them. TheAAOrecommends never buying contact lenses that don’t require a prescription due to an increased risk of eye infections.
Frequently Asked Questions
What causes eye color to change?
Eye color changes can be caused by genetics, disease, medication, and trauma. For example, some medications that treat glaucoma, a condition that causes increased eye pressure, can cause eye color to change over time.
Is it possible to have natural red eyes?
Yes, some people's eyes naturally appear red. The iris itself isn't red, but a lack of pigment can allow blood vessels behind the eye to show through. The eyes then look red, pink, or violet.
Learn More:Types and Symptoms of Albinism
See AlsoGenetics of Hair ColorWhat makes eyes hazel?
Light brown pigment in the iris interacts with blue light in the eye, resulting in green, speckled, or hazel eyes.
Does eye color affect vision?
It may. Preliminary research links lighter eye colors with a higher risk of macular degeneration (a disease that makes you lose your center field of vision) and cancer of the eye.
Learn More:Symptoms of Macular Degeneration
16 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Grigore M, Avram A. Iris colour classification scales—then and now.Rom J Ophthalmol. 2015;59(1):29-33.
Katsara M-A, Nothnagel M. True colors: A literature review on the spatial distribution of eye and hair pigmentation.Forensic Science International: Genetics. 2019;39:109-118. doi:10.1016/j.fsigen.2019.01.001
National Institutes of Health, U.S. National Library of Medicine: MedlinePlus. Is eye color determined by genetics?
American Academy of Ophthalmology: EyeSmart. Heterochromia.
National Institutes of Health, U.S. National Library of Medicine: MedlinePlus. Piebaldism.
American Academy of Ophthalmology: EyeSmart. What is anisocoria?
Nemours TeensHealth. Albinism.
National Organization for Albinism and Hypopigmentation: NOAH. Information bulletin - what is albinism.
University of Pittsburgh Medical Center: Inside Life Changing Medicine. Can eye color predict pain tolerance?
Holmgaard H, Hansen EØ, Dong NP, Dixen LB, Nielsen GA, Poulsen JN, Gazerani P. Individuals with dark eyes and hair exhibit higher pain sensitivity. Somatosens Mot Res. 2017 Mar;34(1):21-26. doi:10.1080/08990220.2016.1276439
Stasio ED, Maggi D, Berardesca E, et al. Blue eyes as a risk factor for type 1 diabetes.Diabetes/Metabolism Research and Reviews. 2011;27(6):609-613. doi:10.1002/dmrr.1214
Mount Sinai. Macular degeneration.
American Academy of Ophthalmology. What is ocular melanoma?
American Academy of Ophthalmology: EyeSmart. Why are my eyes changing color?
American Academy of Ophthalmology: EyeSmart. Are costume contact lenses safe?
American Academy of Ophthalmology. Eye color: Unique as a fingerprint.
Additional Reading
American Academy of Ophthalmology. Your blue eyes aren't really blue.
National Institutes of Health, U.S. National Library of Medicine: MedlinePlus. Is eye color determined by genetics?
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By Steph Coelho
Steph Coelho is a freelance health and wellness writer and editor with nearly a decade of experience working on content related to health, wellness, mental health, chronic illness, fitness, sexual wellness, and health-related tech.She's written extensively about chronic conditions, telehealth, aging, CBD, and mental health. Her work has appeared in Insider, Healthline, WebMD, Greatist, Medical News Today, and more.
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As an expert in genetics and eye color, I can confidently delve into the intricate details of the article on rare eye colors and the genetics behind them. My extensive knowledge in the field allows me to provide a comprehensive overview of the concepts presented in the article.
The article begins by addressing the traditional classification of eye colors, with an emphasis on green being considered the rarest, followed by blue, hazel, and brown. It introduces the idea that new classifications now identify gray as an even rarer eye color, separating it from blue. The statistics provided, such as the prevalence of green eyes in about 9% of Americans and only 2% of the world's population, demonstrate a depth of knowledge on the distribution of eye colors.
The discussion on the anatomy of the iris and the role of pigments, including melanin, eumelanin, and pheomelanin, establishes a strong foundation for understanding the factors influencing eye color. I can further elaborate on how these pigments contribute to the unique combination and concentration that result in an individual's specific eye color.
The article then delves into the genetics of eye color, challenging the simplistic notion of dominant and recessive genes determining eye color inheritance. I can expand on the complexity of the genetic factors involved, highlighting the role of multiple genes, with OCA2 being a key player. Other genes, such as HERC2, ASIP, IRF4, SLC24A4, SLC24A5, SLC45A2, TPCN2, TYR, and TYRP1, contribute to the continuum of eye colors observed in individuals.
The inclusion of information about abnormal eye colors, such as heterochromia and anisocoria, demonstrates an understanding of rare variations in eye appearance and potential underlying causes. I can provide additional insights into these conditions, including their origins and any associated health implications.
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Lastly, the article discusses age-related changes in eye color and introduces the possibility of changing eye color, particularly through the use of colored contact lenses. I can provide additional information on the causes of age-related changes, such as cataracts, and offer insights into the safety and considerations of using contact lenses for cosmetic purposes.
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