Several studies, including one released this past summer, suggest that deer (and likely therefore elk) see blue:
Video: New Study Sheds Light on What Deer See | Outdoor Life
Because of this I have not worn blue when big game hunting in many years. Yes, I know that plenty here will say that they've gotten game when wearing jeans but I don't take a chance.
Also, note that black is generally not a natural color. I'm talking about the same black that we wear on large items such as hats, jackets, etc, and not about small amounts of it as trim. Nature gives us dark grays, charcoal, dark brown, etc but rarely black. Take note next time you're in the woods or field how much black clothing sticks out when in the field. I would suggest that the next time you see a blob of black when hunting it's either manmade or a black bear. So, I also never wear a black item - unless I'm going to be inside a blind where it can help you blend in with black inner walls.
A study - by Gore - showed that their Optifade camo was the "best" for concealment with regard to animal vision. I'd be interested to see a nonbiased study of camo and animal vision but I don't think it will happen. In the meantime choose the one you like best.