There has been some kerfuffle about the choice of a black actor to play Heimdallr in Kenneth Branagh's forthcoming film about Thor (eh? Kenneth Branagh making a film about Thor? What is the world coming to?) - see for instance this article in the Guardian. The kerfuffle is apparently between the politically correct who see this as a laudable example of colour-blind casting and the racists who point out that (a) Norse gods weren't black and (b) Heimdallr is called 'the whitest of gods'.
What no one seems to have taken into account is the fact that the Vikings might have had a sense of humour. It was once pointed out to me by an older gentleman, with extensive experience of male bonding-groups during the war, that nicknames in such groups often mean the opposite of what they say, thus people called Shorty are usually quite tall. Although Snorri does call Heimdallr 'the white god', I think the only poetic source for this epithet is Þrymskviða, that joky poem in which nothing is as it seems, which does call Heimdallr hvítastr ása. Given this, I wouldn't be surprised if Heimdallr was black.