Originally posted by Knight Templar
tsk tsk star wars fans, ya'll knowthe color depends on the corusca gem (Shaft used the sick ass purple saba, hes a masta)
i don't really think it matters, just a choice of prefrence
True that. Lightsabers can be any color; Knight Templar is correct in saying that the color of the lightsaber just depends on the color of the focusing gem. No color does more damage than any other color.
Any Jedi, whether he/she/it is a lightside or darkside Jedi, can have any color he wants provided they have the right colored focusing gem. Just look at Jerec and his cronies from Jedi Knight 1; they are had different color sabers. Jerec uses a red saber, true, but so does Princess Leia in the New Jedi Order books. So seeing a red saber is no guarantee that you're facing a Sith Lord or even a Dark Jedi.
(That was one reason why I was disappointed in Episode II: the scene with 200 Jedi all fighting in the same battle and they only have blue and green sabers? C'mon, where's the color diversity? we've seen in the comp games that had Jedi and in the comics and RPG books? Lucas fumbled the ball on this detail, IMHO. Oh, ok, Lucas DID give Mace Windu a purple saber, whoo hoo.

)
Apparently, however, there is some sort of tradition that Sith lords (Namely, Darth vader, Darth Sidious, Darth Maul and Count Dooku AKA Darth Tyrannus) should wield red-colored sabers. I'm just assuming this, but it seems reasonable. Since the only Sith we ever see from the movies are the above characters, it's reasonable to assume that the Sith tradition of red-only sabers exists (maybe).
So while all Sith use red lightsabers, not everyone who uses a red saber is a Sith (or even a Dark Jedi!).