I remember hearing a black man say on TV once: "Black blood is a powerful thing. All you need is one drop of it to be black."
And he was right. Raising children of mixed ancestry to be colorblind is like fighting an uphill battle. (I'm talking from personal experience here.) White kids see them as "black". They tell them they're "black". Black people see them as "mixed" but accept them as black. So, by a certain age, they begin identifying as black. It's practically unavoidable. As long as they don't judge people according to color, that's what's important.
Obama judges people according to color: His comments about white people in his first book and his membership in the black separatist church - THOSE are things that should offend everyone.