However, it's a different story entirely if you're horrified or upset when you find out that a beloved character isn't white... [I doubt anyone here is like that]

I have to say, the color of Rue's skin is hard to miss. It does make me wonder what it means if a reader is stubborn regarding the whiteness of a character, even given information to the contrary- how many times does that information have to be repeated for it to penetrate? I do think it is a problem if one always assumes that everyone is white... However, without further comdemning information (for example: shock/horror/anger when some found out that Rue isn't white) I'm going to withhold judgment and assume the best of people.