There are various colors on man's eyes.
By the way, what on earth is the color of one's eyes?
It is a color of the place said, "Iris" of eyes. It is generally called the color of the pupil.
The iris has the role to adjust the amount of light that catches one's eye.
The color of the pupil does and the one to decide the color of the iris is an amount of "Melanin pigment" in that.

  A lot of this melanin pigments exist also in the surface and the hair of the skin besides eyes.
It is an important coloring matter that defends us from the harmful ultraviolet rays etc. contained in the sunray and is.
And, the amount of the melanin pigment in the iris is different depending on the climate and the race, etc.
In the country where the sun light is strong to prevent ultraviolet rays being absorbed
A large amount of melanin pigments are accumulated in the iris and it becomes the pupil of the black and tea brown.
The amount of the melanin pigment in the iris is a little, and in the country where which it is opposite, the sunray is weak, and the irradiation rate of sunlight is low
It is said that it will become a brown, blue pupil.