I understand your dilemma. You would hope that people would be over such things, but race does matter to some people. His reaction may be neutral or positive, but there's nothing more embarrassing than showing up and seeing the person's confusion and/or disappointment. You just don't know in this case.

You two are likely to describe yourself before you meet--purely for purposes of identification--but if that doesn't happen, you may want to bring the subject up casually, saying something like, "You know, this is no big deal to me, but just in case it is for you, I want you to know that I'm black." Probably better to know up front how he feels.

One note on internet-dating, though. It sounds like your friend knows this person, but if she met him online and doesn't really, know him, I would suggest that you meet and hang out with him in a public place--bringing your friend along to meet him in the flesh wouldn't hurt. If you like him, more private hang-time could be arranged at a later date.