Human eye colour is determined by two factors - the pigmentation of the iris and the way the iris scatters the light passing through it.

Genes dictate how much melanin will be present in the eye. The more the melanin, the darker the eye.

However, it might seem that in some individuals, their eye colour tends to change depending on the amount of light present.

This is because of the double layer of iris present in the eye. The colour depends on which layer reflects the light.

Approximately 79% of the world's population has brown eyes, which makes it the most common eye colour in the world. After brown, 8%-10% of the world has blue eyes, 5% has amber or hazel eyes, and 2% of the world has green eyes. Rarer coloured eyes include gray and red/violet.

What is the World's Most Common Eye Colour? Eye Colour Percentages

Brown Eyes

Approximately 79% of the world population has brown eyes, which makes it the most popular human eye colour. The brown iris is determined by its pigmentation, and can either appear as dark brown or light brown.

The dark brown iris results from a high concentration of melanin and is common in East Asia, Southeast Asia, and Africa. The light brown iris occurs due to a low level of melanin in the iris and is common in Europe, West Asia, and the Americas.

The pigmentation of the eye is passed from parents to offspring through genetics. However, parents with brown eye colour will not necessarily produce offspring with brown eye colour, as the variation of genes can result in another eye color.

Blue Eyes

Approximately 8%-10% of the world has blue eyes. There is no blue pigmentation in the eye, and the blue colour is, therefore, a result of a low level of melanin in the front layer of the iris.

However, research conducted by the University of Copenhagen in 2008 revealed that a genetic mutation that occurred about 10,000 years ago led to the blue eye and that a gene that prevents the production of melanin in the eye could be passed genetically.

Europe accounts for the largest percentage of people with blue eyes while Finland tops the list of countries with the largest percentage of blue-eyed people at 89%.

Hazel Eyes

About 5% of the world has hazel eyes. The hazel colour occurs due to the combination of melanin and the Rayleigh scattering of the light. Hazel eyes seem to change colour from green to brown and blue.

In some cases, the different refraction of light in this eye may result in a multicoloured iris where the dominant colour depends on the wavelength of the light entering the eye.

Amber Eyes

About 5% of the world has amber eyes. The amber colour occurs due to the presence of a yellow pigment known as lipochrome.

This makes the iris portray a russet/coppery tint and a yellowish/golden colour that may sometimes be confused with the hazel colour. Although it is uncommon in humans, it is common in birds, fish, and canines. 

Green Eyes

Only about 2% of the world has green eyes. The green colour results from a low level of melanin, the presence of yellowish pigment lipochrome, and a blue shade caused by Rayleigh scattering the light reflected.

When all these factors combine the result is a green colour. It is common in Central, Western, and Northern Europe.

Gray Eyes

Gray eyes are sometimes confused with light blue eyes. Like blue eyes, gray eyes are caused as a result of a low level of melanin in the front layer of the iris.

The gray appearance is due to the Mie scattering of light off the darker epithelium. The gray colouring, open close observation, can also show small amounts of yellow or brown. Gray eyes are most commonly found in Northern and Eastern Europe.

Red/Violet Eyes

People with severe forms of albinism often have violet or red eyes. This is caused by the extremely low levels of melanin which allows the blood vessels to show through. The rate of red/violet eyes is extremely rare.

Heterochromia

Heterochromia is a rare case where a person exhibits two different eye colours. Complete heterochromia is when the two irises portray different colours whereas partial heterochromia or sectoral heterochromia is the iris shows two different colours. 

Which Eye Colour is the Most Common in the World?

Rank	Eye Colour	Estimated Percentage of World Population
1	Brown	55% to 79%
2	Blue	8% to 10%
3	Hazel	5%
4	Amber	5%
5	Green	2%
6	Gray	<1%
7	Red/Violet	<1%
8	Heterochromia	<1%