I talked with my child about racism before MLK Day this year, when he'd just turned 3. He was less colorblind than I'd thought.
I mentioned more than once that one reason Obama's election is very exciting is that the United States has only ever had light-skinned presidents and he is the first brown one. I was ready to discuss it further if my son asked questions, but he didn't.
An out-of-town friend who spent election night at our house is light-skinned African-American raised by his mother and white stepfather, so he feels very much the same kind of person as Obama. He was very excited about the election and talking mostly in terms that I thought went over my kid's head. But the day after the election, EnviroKid said of our friend, "He's happy to have a president who looks like him." When he watched Obama's victory speech, he pointed out "brown-skinned people" in the audience. So I think he's pretty aware for his age.
Mostly, we've kept the emphasis on what Obama will do as president, not what group he belongs to. That reflects our values. But it IS important to have a non-white president for a change! We'd be talking about it more if our child were a little older, like 5 or 6; we WILL talk about it more in years to come.
During the Democratic convention, EnviroKid was very interested in the video about Obama's life, showing him with his maternal family. Later I found a photo of Obama with his paternal relatives in Kenya. We talked about how his parents grew up in different cultures and had different color skin, and his skin is an in-between color. I think it's important to acknowledge both parts of Obama's heritage. People tend to see him as black, he identifies himself as black, but his mother and her family were important in shaping him too. He's at least as white as I am Jewish
It's all so complicated! Children need to be aware of race and its role in our history and our present society, but that awareness comes gradually.