If people had a problem with Dooku's lightsaber being purple, then they're really going to hate this change:

http://www.youtube.com/watch?v=_kpPhJvFeIs

Basically, these are my reasons for changing Yoda's lightsaber color (and I talked about this in the Radical Prequel thread as well):

Thinking about the idea of Dooku and Mace having a similar position on the Jedi Council (Grand Master, perhaps?), I'm beginning to wonder if maybe I should also rotoscope Yoda's lightsaber to be purple as well in my EP3 edit (when he dispatches the two clonetroopers who are trying to kill him on Kahshiek). I know some people hate purple lightsabers, but if Yoda, Mace, and Dooku all shared a similar high position on the Council, then maybe their lightsabers should have the same color.

The biggest question that I always had with AotC and RotS was why Mace should be the only one to have a purple lightsaber in the PT (except ultimately there was no significant purpose to it... maybe Lucas did it for s**ts and giggles, I don't know), so why not put his lightsaber's color to an effective use?

I'm not saying that there needs to be a strict or rigid "Ranking System" for the Jedi, not at all. But since Yoda and Mace do seem to be at the very top of the Jedi Order, why not present a visual indication of that higher mastery? (and purple/violet is often regarded to be one of the highest "color ranks" in symbolism, according to some of the esoteric/mystery religions that I've researched and studied)