ORIGINAL: therabbit

This probably isn't going to score me any cool points, but all the bad guys have red/orange/yellow lightsabers because they use manufactured crystals, instead of natural ones.http://www.howstuffworks.com/lightsaber.htm

In the Jedi Order, each Jedi student makes a journey to get Illium Crystals for the lightsaber they will one day build. This journey is considered a rite of passage. As a result, Jedi sabers are many different colors depending on the crystals they find.
There is no such ritual for the Sith. The Sith prefer synthetic crystals for their sabers. The synthetic crystals save the Sith the long trek to get Illium Crystals, provide more blade tuning options, and give Sith sabers their characteristic red blade