Well, it definitely couldn't be blue since blue represents sadness, and running Windows makes me sad.
It couldn't be yellow, since yellow is statistically the favorite color of most insane people (or so I've read), so therefore Yellow must represent BSD, which was brought to us by the folks who brought us LSD.
It definitely cannot be black, since that is representative of the prince of darkness, and as we all know, SCO is the spawn of Satan and must therefore be assigned the color black.
It cannot be white, because white is the color of purity and perfection, and we must admit that Linux is not perfect, nor is any OS. White must therefore remain a reserved color for whatever OS God runs on His computers.
Green? Red? Both represent communists. Although we like the GNU Linux OS under GPL, we're not commies and we don't wish to force everyone else to conform.
Rainbow? Heck no, Linux isn't a gay OS, besides, Linus, the father of Linux, is not gay.
Indigo? Crimson? Gray? All taken by SGI's wonderful visualization workstations, so those colors are right out.
Therefore, we must assign Linux the color <font color="purple">purple</font>, which is the color of royalty, and as we all on here can agree, Linux rules, therefor Linux must be of royal blood.
How do you like my logic?