Eye color is inherited through many genes, not one. Two genes on the same stretch of DNA, OCA2 and HERC2, have the biggest effect on how much brown pigment the iris makes, and dozens of others fine tune the shade. That is why two brown eyed parents can have a blue eyed child. Our free eye color checker reads your own shade from a selfie.
The old rule, and why it is wrong
Many people learned in school that eye color follows one gene, with brown always beating blue. Under that rule, two blue eyed parents could never have a brown eyed child, and eye color would come in only two flavors.
Real families break that rule all the time, and the range of real eye colors, from ice blue to espresso brown with every hazel and green in between, does not fit two flavors either. The simple rule was a teaching shortcut. Research since then has shown that eye color is polygenic, which means shaped by many genes at once.
A 2021 study of almost 195,000 people linked 61 regions of DNA to eye color, 50 of them new. Each one nudges the amount or spread of pigment a little.
What actually sets eye color
Every eye color comes from melanin, the brown pigment, in the front layer of the iris, and from how that layer scatters light.
- Plenty of melanin gives brown eyes.
- A moderate amount gives hazel, amber and green, with help from a yellow tint.
- Very little gives blue and gray, whose color comes from scattered light.
So eye color genetics is mostly about one question, how much melanin the cells of the front iris make and store.
OCA2 and HERC2, the two big players
Two neighboring genes do the most work.
- OCA2 helps the pigment cells make melanin. When it is fully active, the iris holds a lot of brown pigment.
- HERC2 sits next to OCA2 and acts like a dimmer switch for it.
A 2008 study found that a small change inside HERC2 turns OCA2 down in the iris, and that almost everyone with blue eyes in the study carried it. That one change explains a large share of blue eyes. But it does not explain everything, which is where the other genes come in.
Why two brown eyed parents can have a blue eyed child
Each parent passes on one copy of every gene. A parent can have brown eyes while carrying, and passing on, a version that turns pigment down.
If both brown eyed parents pass on versions that turn pigment down, their child can end up with green, hazel or blue eyes. The other genes add more chances for surprise, nudging the shade one way or another.
The reverse, two blue eyed parents with a brown eyed child, is much less common but possible for the same reason. Eye color charts that promise exact odds from two parents assume a single gene, so treat them as rough guides at best.
Why babies change eye color
Many babies are born with lighter eyes than they will have later, because the pigment cells in the iris are still filling up with melanin. Over the first year or two, eyes that started blue or gray can turn green, hazel or brown. Eyes that start brown usually stay brown, because they already hold plenty of pigment.
Most of the change happens in the first year, and eye color usually settles by about age two or three. Small shifts can continue for a few years after that. In adults, eye color should stay stable, so a new change in an adult is worth showing to an eye doctor.
Hazel, green and the in between colors
The many genes that tune eye color are why so many eyes land between the main colors. A little more pigment near the pupil and less at the edge gives hazel or a gold ring inside green. A little yellow tint in a blue iris gives blue green, covered in our guide to blue green eyes. Sometimes the pigment differs between the two eyes, which is called heterochromia, explained in our guide to heterochromia.
Why some eye colors are rarer
Colors that need a narrow balance of pigment are rarer than colors at the ends of the scale. Brown, with plenty of pigment, is the most common color in the world. Green needs a small amount of melanin plus a yellow tint, and only about 2 percent of people worldwide have it. Our guide to the rarest eye colors ranks them all.
Find out your own shade
Your genes set the range, and the light sets what you see on any given day. Our eye color checker balances the light using the whites of your eyes, then reads the color of your iris on your device. It names a shade only. It does not read anything about your genes, your health or where you come from.
For the colors that suit your eyes, skin and hair together, try our seasonal color analysis.
Why DNA tests only roughly predict eye color
Scientists have built tests that guess eye color from DNA. The best known, called IrisPlex, reads a handful of the most important genetic markers. Studies of it found that it predicts blue and brown eyes well, but struggles with the colors in between, such as green and hazel. Those middle colors depend on many genes with small effects, which a short test cannot fully read.
That is the same pattern a photo shows. Blue and dark brown are the easiest colors to name, while hazel, green and gray sit between neighbors and are harder for people and tools alike.
Does eye color change in adults
The pigment in an adult iris stays stable. What changes is how it looks. Light, clothes, makeup and pupil size all shift the color you see, and lighter eyes shift the most. Some eyes very slowly lighten or darken over decades, but a quick or obvious change, especially in one eye, is something to show an eye doctor rather than put down to genetics.
What we found in our own test photos
Photos show the same split that DNA tests do. When we ran our eye color checker on 701 public portraits with a recorded eye color, it told light eyes from dark eyes 68 percent of the time. For exact colors, people recorded as brown were named correctly most often, at 67 percent, then blue at 57 percent, hazel at 38 percent and green at 16 percent. The colors in the middle of the pigment scale were the hardest, just as they are for genetic prediction. The full test is on our methodology page.