I don't think we'll get a green Leech, but I think that's a wise choice. I think they're making Leech out to be some kind of godly figure.
He has a pale, entirely hairless [head included] body. His body is pure, simplistic. The room he is being held in is stark white. Again, pure, simplistic. His power hampers the X-Gene, thus Leech can be said to have control over mutation. I really think they're setting him up as some God-like presence. A being of sheer power.
The white room: These stark white rooms always indicate something special. Something powerful. In the Matrix it was the Architect. In Aeon Flux it was the leader of the resistance via psychic presence. The stark white rooms have been chosen for a reason, and I think it's for that heir of power.
The Beast scene: We see him controlling Beast's mutation, again, like he's god-like. He has the power to change Beast from one extreme to another.
Everyone wants him: The government want him for the cure. The X-Men want him. The Brotherhood want him.
In short, I think they're going to build Leech up as something really special in this movie.