My son looks white but identifies as biracial but is constantly challenged for that fact.
He gets really frustrated and insulted by people not believing him. I try to tell him that most go by his apearence but he gets mad when they challenge his answer.
Once in 2nd grade his friends had a "friendly" basketball game. It so happened that the teams seperated into color, black boys against white boys, with my son among the black boys. Well he got into a fight with a boy from the white team who called him a traitor for not picking the white team.
I knew nothing about this, I guess they settled their differences but a few days later I pick him up and he drags me by the hand down the corridor and shouts "See, I told you I was black!".
It's all preception really and it's too bad that most who ask "what are you" follow up with "really?" or "are you sure?".