Rainbow Cruise texhacking problems.

[Shiroyu]

I'm having some problems with Rainbow Cruise. Namely, the sky(/water) and any of the +2 textures.

I'm trying to turn RC into a wintery night kind of deal, and I would like to know if there is a way to alter the color of the sky into a very dark blue. I'm also curious on how transparencies work on +2 textures, because they don't seem to do anything, even with indexing. (Using Photoshop CS2) I'm trying to eliminate the rainbow and make the trees in the back wintery, but the rainbow is still there and the trees have no transparencies.

If you can help me, I'd really appreciate it.