Well, generally speaking, yes, it happens, but it is rare. It is possible to have different color eyes. And in many cases, there is something to do with the genetic causes of this problem. And also, a blow to the head can damage the tissue that produces brown pigment, making one eye no brown. You should know that the layer of brown pigment covers up other colors, like blue or green. In the absence of the pigment, you can see the underlying color in the damaged eye. So it is common for some people to a blue eye and a green eye. By the way, according to some experts, there is also something to do with the blood passing. Anyway, you can console it with your doctor.