What gives eyes their color
The iris color is determined by the amount of melanin pigmentation. The more pigment there is, the darker the iris will be. Blue, gray, and green eyes are lighter because there is less melanin inside the iris.
By far, the most common eye color in the world is brown, with over 55% of the population falling into this category. Depending on where a person is born, eye color demographics can vary wildly. For instance, nearly all persons of African and Asian ancestry have brown eyes. It’s believed up to 10,000 years ago, all humans had brown eyes only. Then a mutation turned off the pigmentation on the front of the iris.
Hazel eyes are similar to brown eyes, the distinction being these are lighter. A defining trait of hazel eyes is their multi-coloured appearance that can vary from copper to green depending on the lighting. Hazel eyes have a higher concentration of melanin around the iris’ border. Estimates suggest 5 to 8 percent of the world’s population is hazle-eyed (both green and brown).
The next most common eye colors are blue, gray, and green in this order. It’s commonly quoted that only 2% of the world’s population has green eyes. There are also so-called ‘amber’ eyes. which are even rarer than green eyes. Amber eyes or ‘wolf eyes’ as they’re sometimes called are completely solid and have a strong yellowish, golden, or russet and coppery tint. They can also contain a small amount of gold-ish gray. It’s not clear how amber eyes form but some suggest it’s due to the increased presence of a pigment called lipochrome (also known as pheomelanin).
Lastly, people with albinism, a condition that causes a complete lack of or very low levels of pigment in the skin, hair, and eyes, sometimes appear to have violet or red eyes. Because albino people essentially lack pigment in the iris, light simply bounces off the back of the eye. Albino eyes may appear red because the light reflected first off blood vessels at the back of the retina. This is the same reason why you sometimes appear red-eyed in photos. The eyes can appear violet in certain lighting conditions when the red color mixes with the bluish color resulting from light-scattering effects — basically for the same reason why the sky is blue.
