A week or so ago, there was a bit of a brouhaha over the race of the characters in the movie Hunger Games. I participated in a discussion of it on the Skull Honey blog.
While I think that there could be more non-white characters in fiction, the truth is that a person is not the color of their skin. Underneath the surface of skin color, eye color, hair color, etc. we're all the same. We all want to be happy. We all have had experiences in our lives that have shaped who we are. You can give two people the same life experience and given the differences in their personalities, they will respond differently and come out of the experience changed or not and in different ways.
So, the character of Rue in The Hunger games has dark brown skin and eyes, and from that description the reader is supposed to leap to the conclusion that Rue is African-American. But there are other ethnic groups in the world who have dark brown skin and eyes: Native Americans, Arabs, Italians, Greeks, Latinos, Polynesian, Indians, etc. If dark brown skin and eyes is all I have to go, I can not determine what ethnic group the character belongs to. I don't have enough information.
Even if I have enough information to determine that Rue is African-American, that does not tell me anything about her character. Expanding that out into any novel, skin color tells me nothing about the person's character. Someone who is African-American could have grown up in the ghetto, but they also could have grown up in a middle class neighborhood or an upper class neighborhood. Most of the African Americans that I have been acquainted with are professionals. They're doctors, lawyers, engineers, teachers, etc.
Many writers describe a character's eye color, hair color, skin color, and other physical characteristics. Unless it is put into some sort of context, none of those details tell the reader much about who the character is, what they want, what their goals are, what their personal demons might be.
It's something to think about.