This guy walks on the bus and … proceeds to ignore everyone around him. (Probably a good idea.) We may not know much about him, but we do learn a lot about Julian.
Because he's well-dressed and carries a briefcase, Julian assumes that he holds a respectable position and decides to make friends. But Julian has the social skills of a sea cucumber—if that—and has no idea what to say to the guy. So, he asks for a light. When the man gives Julian a packet of matches without looking away from his paper, we get the feeling that he has no interest in chatting.
In fact, when Julian hands the matches back to him without taking one, the man lowers his paper and gives him an "annoyed" (70) look. The well-dressed black man is either completely oblivious to the white passengers, or he has no desire to interact with them. Either way, his lack of enthusiasm could stem from many things—not wanting to talk, not liking Julian, not liking white people. Or even all three.