Just reading this thread and as usual, I agree with Missy. I would recommend a book entitled, Shades of Black. While it is geared toward raising the self-esteem of black children, I think the message is relevant for any child learning to appreciate difference. It's a fun and sends a positive yet subtle message. Good luck Kama!
I remember really like how Beverly Daniel Tatum discussed race with her son in her book: "Why Are All The Black Kids Sitting Together in the Cafeteria?": A Psychologist Explains the Development of Racial Identity.
(I'd summarize, but I have boobie brain and it's inhibiting my recall function.)