this question has been answered many times... but ill repeat it cos... well im bored, and it makes me feel clever
you are obviously compareing Windows 32bit to linux's 24bit and thinking linux is lacking.
here is what 32bit colour is...
8bits of RED
8bits of GREEN
8bits of BLUE
8bits of APLHA
where ALPHA is a fancy word for Hardware Transparency.
in windows, when you are not playing a game, or looking at a screen saver, ALPHA is not being used... any transparency you do see is eing emulated with software.... the same for Linux...
on the desktop, ALPHA is not used...
the only difference, is in Linux... everything works with only 24bits.. (RED GREEN BLUE)
in windows, although all 4 channels are being used... ALPHA is perminantly set to 00000000.
fireup a game in windows, and suddenly, the last 8 bits are put to use...
fire up a game in linux, and colour jumps into 32 bit mode.
think of it as Windows saying "I have 5 fingers"
and linux saying "I have 4 fingers.... and a thumb"
you linux desktop is capable of showing just as many colours as windows
the configureation you are seeing is limiting you to 24bits, befause at the moment, the desktop does not support hardware accelerated transparency.