Why do our eyes have a different color?

primary colors

blue
  Eye color - a characteristic determined by pigmentation of the iris. The iris consists of ectodermal and mesodermal layers. From the distribution of these pigments and depend on the color.

grayIn contrast, blue eyes, in this case, the density of the fibers of the external layer above. Because they have a whitish or grayish color, the color is not blue, and blue. The greater the density of the fibers, the brighter the color. Blue eye color - is the result of mutations in the gene HERC2, due to which the carriers of this gene reduced melanin in the iris. There was this mutation is approximately 6-10 thousand years ago, so that all people with blue eyes may be related.

Few of the science of blue eyes:
"Originally, we all should have been brown eyes," - said in a university news release Eiberg, professor of the Institute for Cellular and Molecular Biology (Institut for Cellulær og Molekylær Medicin).

However, occurred about 10 thousand years ago, a mutation that affected the gene OCA2, has led to the fact that the production of melanin in the iris of the eye was limited (and brown color was "diluted" to blue).

 Definition of gray and blue eyes is similar, only with the density of the fibers is even higher and closer to their shade of gray. If the density is not so great, the color will be blue-gray. In addition, the presence of melanin or other substances gives a small yellow or brownish impurity.


green

Green eye color is determined by a small amount of melanin, also may play a role here red hair gene. In the outer layer of the distributed yellow or light brown substance, which may be associated with a particular disease. Because the back layer is blue, the result is green. Coloration of the iris is usually uneven and sometimes a lot of different shades.


amber

 Amber eyes are of monotonous pale brown and yellowish-green, sometimes slightly reddish tint. Sometimes the color they are close to the marsh or golden. This causes the pigment lipofuscin.


swamp

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 Swamp eye color, in English terminology is called peanut (English hazel), is a mixed color. Depending on the lighting, it can seem a golden, brown and green and brown. In the outer layer of the iris melanin content rather moderate, but it often contains other substances. In contrast to the amber color in this case is not monotonic, but rather heterogeneous.


brown

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 In this case, the outer layer of the iris contains a lot of melanin. Therefore, it is absorbed by low-frequency light and reflected light for a total of brown. The higher concentration of melanin, the darker the eye, in some cases it may be almost black.


red

Red eye color is found only in albinos. It is associated with the absence of melanin in the iris, so determined in the blood vessels of the iris


Multi-colored - heterochromia

Heterochromia - a difference in the color of the irises (as well as hair or skin). It is the result of the relative excess or lack of melanin (pigment).

Eye color, that is, color irises, is determined primarily by the concentration and distribution of melanin. Heterochromia affected eye may be hyperpigmented or hypopigmented.