The interesting issue in this topic is when they will be aware of the implications. Let me explain what I mean:
My daughters grew up in a pretty white only area, having only 1-2 black kids in their class while in K-6. For them race or color was not an issue at all, they knew that these kids were different, but it neither bothered nor interested them. They played and interacted with them just as they did with white kids or asian kids (of which they had quite a lot in class.)
It changed when they started Middle School (or as some call it Junior High). Not only were there many more black boys than they had ever seen before, they also now knew about sex and dating and the important issues of being within acceptable boundaries when it comes to peer behavior. So in the beginning they had some issues like yes, I want to date, but no, I can't date a black boy because my girlfriends will not accept that. However, and that was the funny part, my daughters being pretty rebellious at that time soon switched sides completely: they sought to date black boys just to rub it into their white friends' faces (they might have thought they could shock me as well, not knowing that my hubby and I already were very much into IR).
So things developed kind of naturally, the very short "white-only" date period was followed by a very strong and wild "black only" period, then a short "I don't care what color as long as the dude is cool" period and now both are safely established with their black boyfriends (may be because black boys are "much cooler").