There's Red and Blue, but why not Yellow?

[ZeronosVega]

This has always been a curiosity of mine, but have you ever wondered why there isn't a Yellow Mage? I guess it's because I see Red and Blue, and think of the primary colors. But, just to make for interesting discussion, if you were to design a Yellow Mage Job, what would it do?

One interpretation I've seen of a Yellow Mage is through the Final Fantasy Tactics A3 project, found here. In it, Yellow Mages gain their abilities by copying from the "enlightened races" instead of monsters a la Blue Mage.

Anyway, feel free to discuss.