Jason, I initially disliked the notion of Yoda having a purple saber, but the more I think about it, the more it makes a brilliant kind of sense. Putting Yoda, Dooku, and Mace on the same level like that heightens the dramatic tension and also dispels the "huh??" effect upon seeing green & blue sabers galore, but only one purple blade. I'd definitely encourage you to pursue this idea, radical though it may be.
Looking forward to your edits! :)