The most common eye color is brown. About 80% of the world's population has dark eyes! About 10% have blue eyes, about 5% have hazel eyes and only 2% of the world's population has green eyes!
Where does the color of the eyes come from?
The iris, the colored part of the eye, controls the diameter and size of the pupil (NB: this is why some contact lenses have diameters larger or smaller!). The iris has melanin and it is thanks to two factors that it is pigmented more or less. The first factor is genetics, of course if everyone in your family has dark eyes you will necessarily have dark eyes (unless a great aunt had very clear eyes and the magic of genetics has operated!). The second factor is the melanin content, it will influence the diffusion of light as it passes through the eye!
How does melanin affect the color of the eyes?
The color of the eyes is the result of a mixture of melanin variations. For example, if a person has a small amount of melanin, his eyes will be blue. An average amount of melanin will give green eyes and a large amount of brown eyes!
Some people have different color variations in their eyes. We can often see people with blue eyes with a green outline or brown around the pupil, it is different parts of the iris that create different amounts of melanin depending on the location of the eye!
How do the genes that manage the color of the eyes work?
Our genes require an iris cell to produce a given amount of the black pigment so called melanin. The more melanin produced, the darker the eye color will be. Genes that generate large amounts of melanin are dominant over genes that make small amounts of melanin (those that create blue eyes).
Did you know ? The production of melanin does not start at birth, that's why newborns have blue eyes. It is only from the age of 3 that children have their final color.
Can the eyes change color?
You have already noticed that in some people the color of their eyes change depending on the light. The reason ? The iris has two layers. In people with light eyes, the first layer contains little melanin. So according to the external light, the eyes will seem to change color when the light reaches each layer.
The change of light can affect the size of the pupil; which expands in the darkness and contracts in strong light. As the size of the pupil changes, the iris pigments expand or contract, giving the impression of a slight change in color. Strong emotions can also change the size of the pupil (when you are in love or angry for example).
Eye color may change with age, especially in people with light eyes. Exposure to the sun can make your eyes look darker, like your skin in the summer.