Color depth not respected in all games
My desktop runs in 24-bit mode (highest setting in nvidia-config) but I noticed that in games like Red Eclipse and Sauerbraten (Cube2), my color depth is not respected. The color depth option in those games is set to 24 or 32-bit but it always looks like 16-bit is being used. Colors in textures looks crappy and also background of menus look like ****, they become pixelated. When I open the background image in an image viewer, it is displayed correctly, but as soon as I start the game, it looks like crap. Other games like Xonotic, Doom 3, Quake 4, ... don't have this issue.
64-bit Arch Linux fully updated (188.8.131.52 kernel + Nvidia 270.30)
AMD Phenom II X4 955
6GB DDR3 RAM
Geforce GTX 470
Also previous versions of the driver had this problem. I tried with enabling or diabling certain options in xorg.conf, but without success. 2D engine runs fine on 24-bit depth, but the Cube2 engine powered games suffer from this weird phenomenon. Other game engines work correctly. I was thinking about a problem with SDL (because that's what Cube2 uses), but Xonotic-SDL is not affected.
Any more tips or could this be a bug? If you need screenshots or config files to clarify this issue, don't hesitate to ask me. Thanks for all help.