The teams were initially divided into four racially segragated teams. During the third week the original teams were broken up into two diverse teams. From this new makeup the teams ceased operating on purely racial terms seeking to find alliances that were selfishly advantageous.
Thats not to say that race won't or doesn't come into play. I'm sure that in the final weeks of the show there will be some appeals to common ancestry, but early in the game we saw a white tribesmen vote against a white tribesman and black tribesman vote against a black tribesman. Racial overtones won't come into play (in my view) until the game is really zero sum. At this stage every trick will be played - but it will have nothing to do with race and everything to do with winning.