Something I heard a few times from IT guys (none of which are programmers) is that the color black uses more memory than the color white, so users should set their desktops to white, not black.
To be honest it sounds silly to me and I can't wrap my head around why one color would use more memory than another. Every once in a while I google about this to see if anyone else is talking about it, but I wanted to hear from someone who knew more than I do on the subject.
I'm less curious if it's possible, because I think it's total BS, and more curious if anyone else has heard this.
-- Not an April fools joke.
On the off chance you're actually serious...
Colors are usually stored via their pixel values via their Red, Green, and Blue components (RGB), as that's how our displays work. (Print work is often handled by storing Cyan, Magenta, Yellow, and blacK pixel values, in the CMYK mode.)
Regardless of color depth, whether it is 15 bit, 16 bit, 24 bit, or 32-bit, it takes the same amount of memory to store black (0x000000 for 24-bit) as white (0xFFFFFF). Both can compress equally well, too. (Any solid color background can compress very well; limited-color backgrounds can compress well.)
My guess is your friends prefer black because it is easy on the eyes. (At least, that's why I prefer black backgrounds, black background colored terminals and text editors, etc.)