That's just silly.
Do you guys really think that there is a deeper meaning behind Mace Windu's saber? Sam Jackson wanted purple, and he got it, as simple as that. And saying that Mace Windu isn't properly in tune with the light side of the force is just idiotic. He's supposed to be one of the greatest Jedi at the time, not some substitute for Yoda. Besides, in twenty years' time, he'd be nearly dead himself. You don't get on the council if you're having second thoughts.
AND besides, "alignment" in terms of Star Wars is a game construction. You can't superimpose KOTOR terminology on movies, which are visions of an imagined "real" world.