True, but then why didn't Obi-Wan have a green saber? Would we then have to go back and recolor his from Episode 4? The line of logic in changing the colors of people's sabers other than Dooku's takes us to some pretty dark territory, and I'd rather not explore it. Changing Dooku's saber has a significant impact on the story, but to me trying to come up with some kind of system for who should have what color lightsaber just ends up as a tedious mess. I think this is an example of "just because Lucas signed off on it does not mean there's something wrong with it." :P
Anyway, I do agree though that blue would be fine for Dooku's saber. Let's let Mace be the one with the weird lightsaber, hehehe.