I definitely had something important missing from my worldview as a kid - I'm not white, my family isn't white, I didn't even come up in a white neightborhood, and still I managed always to imagine nonwhite characters as white. You know Cassie, from Animorphs? I imagined her as white until the book 4 cover showed her as black, even though the text explicitly described her as black (it didn't make a song and dance out of it, which was necessary for me back then). I'm much better about that now (I saw Shadow as mixed on the first read), but white-as-default in Western culture is so powerful that I try to give people some slack for making that mistake. I mean, so long as they don't get tetchy about it like in the "lol I didn't see it so it must not have been there" comment in the secret.