If he were the guy who was black, why would it be offensive. It's like those Question Time episodes where the host is too scared to describe the person he is trying pick on to ask a question : "yes, you, the person, the person over there, the person in clothes, you in the audience".
I have my mates round from time to time, and I'll reference them, but of course my family don't know who each of them is verbatim, so when they ask 'who's that one again', and I say the 'mixed raced girl', is that racist? Or should I go "ah yes, the person, the person who came to the house, the person who I'm friends with, the person who worse some clothes?