Human eye color comes from melanin, the same compound that determines skin and hair color.
Melanin absorbs light, even some UV light, which is important for the iris — the part of the eye that controls how much light enters the pupil.

Melanin and Pigment Types

There are two different types of melanin a person could have in their irises: eumelanin, which produces a rich chocolate brown color, and pheomelanin, which produces a range of amber, green, or hazel colors. Blue eyes, on the other hand, get their color from having relatively little eumelanin. The pigment itself isn’t blue, but the way the light scatters around the front layer of the iris ends up appearing blue — the same way the sky appears blue.

Green eyes come from a combination of both types of melanin in low enough levels to also get a bit of the light scattering effect. Hazel eyes have enough melanin that they don’t get the light scattering effect. Red and “violet” eyes (very rare) come from having almost no melanin at all, so you actually see the color of the underlying blood vessels or it combines with the light scattering effect to produce violet. This is typical in albinism.

How Common Are Different Eye Colors?
Living in an English-speaking country, it might seem like different eye colors happen at a similar rate, but across the world, this is not the case at all. Brown eyes are by far the most common.
• 70-79% of people have brown eyes.
• 8-10% have blue eyes.
• 5% have hazel eyes.
• 5% have amber (very light brown) eyes.
• 3% have gray eyes.
• 2% have green eyes.
• Less than 1% have red or violet eyes.
• Less than 1% have heterochromia (partly or completely different-colored eyes).

Eye Color Genetics Is Complicated

We used to think that eye color is determined by just one gene, but in recent years scientists have found that it’s actually many genes acting in tandem, and tiny tweaks to any of those genes can result in a different color. There are two genes that are strongly associated with eye color, but as many as 16 play some role in it. That means it’s not so easy to predict a child’s eye color based on their parents’. Blue-eyed parents won’t always produce only blue-eyed children.

Blue Eyes with Babies

Many babies are born with blue or gray eyes but then develop a different eye color as they get older. This tendency is most common among Caucasian babies. The reason a baby doesn’t always have their permanent eye color yet when they’re born is that the cells that produce melanin sometimes need light to trigger melanin production, which obviously won’t happen until after they’re born.

Other Ways Eye Color Can Change

Some people may claim that their eye color changes from day to day, but this is likely due to how their eyes reflect the color of the clothes they choose each day. Eye color can appear different if the pupil changes size or if the person is in bright or dim light. Apart from the gradual change over time if their eyes produce more melanin as they get older, an eye injury could cause a permanent eye color change.

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