Quote Originally Posted by Serapy View Post
Is this some sort of power source?
Yes.

But these games weren't made for science fiction fans; in other words, there's really no explanation. They never even explain how Squall's gunblade works, and you use it through the entire game.

I'm sure you've heard of the Ultimecia theory (of course; you're posting this question), so let me post a new idea: maybe, the colors are symbolic, not literal. Maybe it's an expression of Ultimecia's pain (or, maybe Squall's?). Or her disgust.

Or, it just looks cool.

That wasn't meant to be mocking. If anyone can do something to look cool and then later give a plausible argument for it, it's Square Enix.