There are two ways of defining whether someone is black, white or bi-racial.
You ask them how they define themselves.
However, if you are not in a position to ask them, ask yourself this simple question. If Lewis Hamilton worked on the floor above you in your office/business/shop, and someone came in asking to speak to him, would you say
"He's the young black lad who's bay is over towards the window"
or
"He's the young bi-racial lad who's bay is over towards the window"
or
"He's the young light brown-ish lad who's bay is over towards the window"
or
"I don't work here mate. I'm only fixing the air conditioning"