Why some eggs are brown and others white?

It may seem simplistic, the question about the color of eggs, however many are…
those who have wondered about what they see on the shelves of supermarket eggs are brown in various shades, and white.
Why is this different coloring in the shell? Is different the eggs in terms of nutritional properties?
This, therefore, determines to a great extent the color of the egg shell is genetic reasons, and more specifically the breed of the hen. There are different kinds of chicken which, however, are mixed between them. During the creation of the egg has a white shell, however, during the journey to the fallopian tubes of a chicken, χρψματίζεται of a dye, the species of chicken that they have.
An empirical way to see what eggs does a hen is to observe the lobe of the ear. When the pod is reddish produce brown eggs, while when it is white usually produces white.
Why some eggs are brown and others white?
It is worth noting that no difference in the nutritional value of these two eggs is not there, after white and and have the same ingredients and the color does not affect in nothing the vitamins and proteins they contain.