Human eyes come in six main colors: brown, blue, hazel, amber, green, and grey. Brown is by far the most common, accounting for 70% to 80% of the global population. From there, the numbers drop sharply, with blue at 8% to 10%, hazel and amber each around 5%, and green at roughly 2%. Grey, violet, and red-appearing eyes exist too, though they’re rare enough that solid global estimates are hard to pin down.
Brown Eyes
Brown is the default human eye color, and for good reason. The iris contains high concentrations of a dark pigment called eumelanin, which absorbs most incoming light and gives the eye its rich tone. Shades range from very dark (almost black) to a lighter, honey-tinged brown. Because of the extra pigment, brown eyes offer more natural protection against UV light, and people with darker irises have a lower risk of eye melanoma compared to those with lighter eyes.
Blue Eyes
Blue eyes contain very little melanin. The blue color isn’t actually pigmented into the iris. Instead, it comes from the way light scatters through the collagen fibers in the front layer of the iris, a phenomenon similar to why the sky looks blue. The collagen fibers in blue irises are fine, sparse, and uniformly arranged, which favors shorter (bluer) wavelengths of light bouncing back toward the observer. Roughly 8% to 10% of people worldwide have blue eyes, with the highest concentrations in northern Europe.
Green Eyes
Green is the rarest of the common eye colors, found in about 2% of the global population. Green irises have a small amount of melanin combined with the same light-scattering effect that produces blue. The result is a blend: scattered blue light mixing with a touch of yellowish pigment to create green. People of northern and central European descent are most likely to have green eyes, though they appear in other populations as well.
Hazel Eyes
Hazel eyes are a patchwork. They typically combine brown near the pupil with green or gold toward the outer edge of the iris, and the dominant shade can seem to shift depending on lighting, clothing, and even pupil size. This isn’t an actual color change. It’s a trick of how ambient light interacts with the uneven distribution of pigment in the iris. About 5% of people worldwide have hazel eyes.
Amber Eyes
Amber eyes have a warm, golden-to-copper tone that’s easy to confuse with light brown or hazel, but the underlying chemistry is different. Where brown eyes get their color primarily from dark eumelanin, amber eyes contain very little of it. Instead, they’re rich in a yellowish pigment called pheomelanin (sometimes called lipochrome). That high pheomelanin, low eumelanin combination creates their distinctive solid gold appearance, without the green flecks or color variation you’d see in hazel. Around 5% of people have amber eyes.
Grey Eyes
Grey eyes are often mistaken for blue, but they have a distinctly different structure. The collagen fibers in grey irises are denser, slightly thicker, and more irregularly arranged than those in blue irises. This changes how light scatters: instead of favoring the vivid blue wavelengths, the denser matrix diffuses light more evenly, producing a muted, silvery, or steel-toned appearance. Grey eyes can also appear to shift slightly blue or green in different lighting conditions.
Red and Violet Eyes
True red or violet eyes are extremely rare and almost always linked to albinism, a condition where the body produces very little or no melanin. When the iris has almost no pigment at all, light passes straight through it rather than being absorbed or scattered. What you see is the red color of blood vessels inside the eye showing through. In some lighting, a tiny amount of residual light scattering can mix with that red to create a violet appearance. Outside of albinism, genuinely red or violet irises essentially don’t occur.
Heterochromia: More Than One Color
Some people have two different eye colors, a trait called heterochromia. It comes in three forms. Complete heterochromia means each eye is an entirely different color, like one brown and one blue. Sectoral heterochromia means a wedge-shaped section of one iris is a different color from the rest, like a slice of pie in a contrasting shade. Central heterochromia produces a ring of one color around the pupil with a different color filling the rest of the iris, often creating a sunburst pattern.
Most heterochromia is harmless and present from birth. It can also develop later in life from eye injury, certain medications, or conditions affecting pigment, so a new color change in one eye is worth getting checked.
How Genetics Determine Eye Color
The old rule that “brown is dominant, blue is recessive, and two blue-eyed parents can’t have a brown-eyed child” is outdated. Eye color is polygenic, meaning many genes contribute to the final result. Two genes on chromosome 15, called OCA2 and HERC2, play the biggest role. OCA2 helps control how much melanin the iris produces, and HERC2 acts as a switch that can turn OCA2’s activity up or down.
At least eight additional genes fine-tune the outcome, some of which also influence skin and hair pigmentation. This is why eye color runs on a continuum rather than falling into neat categories, and why two blue-eyed parents can, on rare occasions, have a brown-eyed child. The interplay of all these genes means siblings from the same parents can end up with noticeably different eye colors.
When Eye Color Develops
Most babies are born with blue or grey-looking eyes regardless of their eventual color. That’s because melanin production in the iris ramps up gradually after birth. Color typically starts shifting between 3 and 9 months, with the most noticeable changes around 6 months. But the process isn’t always fast. It can take up to three years for a child’s permanent eye color to fully settle in. If your toddler’s eyes still seem to be changing shade, that’s normal.
Why Eyes Seem to Change Color Day to Day
If you’ve ever noticed your eyes looking greener one day and more golden the next, you’re not imagining it, but your pigment isn’t actually shifting. Changes in pupil size alter how much of the iris is visible, which can make the color appear lighter or darker. Ambient lighting matters too: warm indoor light brings out gold and brown tones, while overcast daylight emphasizes blue and grey. The colors of your clothing and makeup can also reflect off the surface of the eye, subtly shifting its apparent hue. This effect is most dramatic in hazel and green eyes, where the balance of pigment and light scattering is already complex.
Eye Color and Health Risks
Lighter eyes aren’t just a cosmetic difference. Less melanin in the iris means less protection from ultraviolet light. People with blue or green eyes have a higher risk of uveal melanoma, a cancer that forms inside the eye. UV exposure from sunlight and tanning beds further increases that risk. Wearing UV-blocking sunglasses is a simple, effective way to reduce it, especially if you spend long hours outdoors. Darker irises aren’t immune to UV damage, but the extra pigment provides a measurable layer of defense.