The title says it all. There are dozens of different colored G-shocks from glossy pink to matte black but I bet there are colors you'd want that haven't been made yet.
For me, I've bought some RIT in denim blue and some orange dye to attack a white bezel/strap set as soon as I get to it.
I also think a cream and a brown G-Shock could look really good. At the same time I'd be interested to see a G-Shock on a nice leather strap. Did they ever make that?