How could you miss Vivi from the list of black mages? He's the quintessential black mage! Only black mage in the series besides nameless mages (well named by the player) to wear the black mage garb.

Black Mage - Vivi's definitely my choice here. Best character in FFIX, one of the best in the series.

White Mage - Aerith. Don't know how well she fits the category, since she can learn anything like everyone in FF7, but Holy and her Limits seem good enough. She's the hero of FFVII.

Blue Mage - Probably Quistis. She's one of the better characters in FF8, which is one of my favorites in the series. I also don't see what all the Kimahri hate is about though and he'd probably be my second barring someone I forgot. Strago and Quina probably are more closely aligned to the class, but I just don't like them as much as characters.

Red Mage - Rydia. I see how Rydia fits the categories you set, but Summoner is really a separate class of FF mage. Also, she loses White Magic later, and has only a couple semi-white magicy summons, which makes this classification even more dubious. I'd say she's closer to Black Mage than Red Mage, really. Still, if we're calling Rydia a Red Mage, then she's my favorite of the bunch. A kickass mage who can easily kill off the party and level herself once she learns Bio/Virus, she saves the party from Golbez when she returns. The last of a group of mages Golbez (and presumably Zemus by extension) feared enough to wipeout even though they didn't have a crystal. Face it, Rydia is a total badass.