Just leaf through the
SM codex. There is something along 6-8 pages dedicated solely to different chapter color schemes.
As you don't want to go with the smurf look, just pick something not blue. I'd suggest going with White Scars, Imperial Fists, or The Mentors. The problems with these are the White scars are fairly monochrome and are a biker chapter, the Imperial Fists would meet your fluff but the yellow-red scheme is very striking and may look ugly to some (and reduce the appeal of them being in a showcase) and the Mentors while they have an interesting scheme, are lacking fluff by comparison. I did find a lexicanum article on them though.
http://wh40k.lexicanum.com/wiki/Mentors#.UGX4fVHp7Jk
If they are going into a display case, I suggest picking a chapter with two primary colors on it and avoid the metallic color schemes. While shiny is nice, too much is very terrible (except on Necron). Monochrome also makes the army look dull.