I don't know about other JUer's children but I think my children really don't take notice of the color of skin. As an example, my 9yr old was talking about the different holidays and mentioned that one classmate celebrates kwanza and another celebrates Ramadan. I knew the girl who celebrates Ramadan but had to ask who celebrates kwanza. I expected he would either name a name or have a physical description. Instead he responded "the kid who's allergic to peanuts".
Our area is very diverse and my kids have been around people from literally around the world. Our last neighborhood included families from China, India, French Congo, Italy and Macedonia. And that just includes the ones we knew. Our family has had house guests from England, Italy and Finland. Close friends just got back from a year living in Korea. I barely knew anyone outside of Michigan growing up!
I do think that racism is a pretty foreign concept to many children growing up in America today. I wish I could say I think racism is almost dead. I think there are those who will keep racism alive forever either in the name of hate or in the name of racial pride. I do think we have come an enormous way in looking at each other as merely fellow human beings.