This seems like such a hard problem to really solve, since so much of what we consider racism, or at least borderline racism, has a significant basis in fundamental human thinking. I really feel for the guy, but it's hard to know where to start.
I try really hard to ignore color, but I'm not immune to at least noticing. Then I try hard not to double-take. It's completely expected to meet Indians at the workplace, but black people are so rare that it always feels like a surprise. Maybe there's a bit of a chicken-and-egg problem in play.
I recall that when I was in the military, I got so used to the racial make-up, which has a lot more representation from black people than my hometown, that it wouldn't register at all. Just another guy. When it really hit home was after I'd been back in Oregon for a few months after I left the service, when I was walking across the college campus and noticed a small group of black students walking towards me. I noticed them, and then I realized that I had just noticed them, as if they were noteworthy. That was the moment I realized how white Oregon [mostly] is. I didn't feel negativity towards them, but I felt uncomfortable that it was something that even came to mind.
In any case, we have two black guys on our team. Both really nice, but very different people. One of them acts like he was raised locally in a wealthy family, he's very laid back and doesn't seem to feel out of place. The other guy is a little older, and if you didn't know better you'd think he was a little hostile. No, he's wary. He acts like he's faced judgement his entire life and he's always waiting for the other shoe to drop.
Easy to be comfortable around the first guy, much harder around the second guy. I want to act like it's not even anything to be aware of, but that in itself seems pretty dishonest. People are different, and that's totally okay. Good in fact, since they bring their own unique perspective to the daily problems we are asked to solve.