White Mage - Y'shtola, FFXIV
Sure, she starts out a bit stale, but over time she gets more and more enjoyable as a character, and gets some great moments in the story.
She's also a catgirl.

Black Mage - Vivi, FFIX
Nothing to be said here

Blue Mage - Quistis, FFVIII
Honestly, I'm not a fan of the personality of any of the series' blue mages. Maybe FFXIV will change this at some point
Anyway, that's why Quistis wins, at least she's a looker.

Red Mage - Alisaie, FFXIV
Again, starts out pretty stale, but both her personality and combat powers grow steadily over the course of the game and its expansions, so she's pretty badass now.