Its up to you how much of it you want to believe, but the book Black Like Me covers the story of a journo named John Howard Griffith who, for reasons known only to him, got a doctor to give him heavy doses of an anti-vitiligo drug and spent a long time in a tanning booth to make his skin dark enough that he could pass for black. He then spent six weeks doing just that, talking very little since he wasn't confident in his ebonics.
The book doesn't allege much that's very sensational to be honest. Just that white people gave him unpleasant looks and generally regarded him with a snobbish attitude, and that blacks were hilariously terrible at figuring out that he wasn't one of them. Apparently another guy, Ray Sprigle, did something similar ten years earlier, but in his case its not clear how he managed to pass as black.
Apparently if you want to do this to blend in, its possible, but the treatment will eventually wear off. In Sprigle's case he might have just darkened his face with makeup or something too, so I suppose it really depends on just how much scrutiny you're actually put under.
