One saber color change I wouldn't mind would be Dooku's, especially if you've removed direct references to his Darth Tyranus/Sith alter-ego. It would help make him a more complex character, and make you think on a re-watch that maybe his conversation with Obi-Wan in hover-jail was him being 100% honest, and maybe the separatists were actually the *good* guys...

Of course, this breaks continuity with The Clone Wars even more than changing Windu's saber color does.

(I'm also all for yellow sabers. I got a little over-excited during season 3 of TCW when Ahsoka lit up her second lightsaber ... and it was yellow! So happy yellow lightsabers are canon, and I'd love to see more of them.)