White is Minwu for easily being the best character of his game, and for often being forgotten as one of the few male white mages. I like how his outfit is different from the typical white mage garb as well.

For black I'll go with Terra. I haven't played much of VI but from what I did get through she seemed alright and it was nice to have a female protagonist? for a change.

Blue will be Quistis simply because the only other named one I'm familiar with (outside of assigning the class like in V) is Quina, who I really didn't think was the great of a character. Would Kimahri from X count for this since his lancet into stealing skills for his ult is kind of similar to how blue mages learn their magic by getting hit by it?

For Red I'll go with Rydia since I always thought she was a pretty cool character.