The tv spot was too bright, that was (I HOPE) the problem, look at Mystique, Beast and the Alcatraz scene too, they all look more white/bright than we've previously seen! It was probably the poster's brightness/contrast settings on his TV/camera that were off.
I wish they'd show us the hi res tv spots because I'm slightly worried - I LOVE how Iceman looks in the above pic, blue and icey looking but in the spot he looks too frosty and white. As said though I'm sure the above pic is(HOPEFULLY) how he'll actually look in the movie!