Dominance is the ability of a genetic trait to over power another. Brown hair is dominant over blond. Brown eyes are dominant over blue. It doesn’t mean that a child of a brown eyed parent and blue eyed parent can never have blue eyes, it just means that it is more likely that brown eyes will prevail. Even if the eyes are not brown, the blue eyes will have a deeper or darker tone than the parents. Sometimes, not always of course. There really are no exact sciences when it comes to our amazing human bodies.