Why is Maniac confused about the color thing or what is he "blind" to?

Maniac is blind to the reasons for prejudice, he is oblivious to the things that make him different..... at least for awhile anyway.

Maniac kept trying, but he still couldn't see it, this color business. He didn't figure he was white any more than the East Enders were black. He looked himself over pretty hard and came up with at least seven different shades and colors right on his own skin, not one of them being what he would call white (except for his eyeballs, which weren't any whiter than the eyeballs of the kids in the East End).
Which was all a big relief to Maniac, finding out he wasn't really white, because the way he figured, white was about the most boring color of all. But there it was, piling up around him: dislike. Not from everybody. But enough. And Maniac couldn't see it.
And then all of a sudden he could.