[Apollonian]

And of course there's Warhammer's Winds of Magic, each of which has a color:

White: Wind of Hysh, Lore of Light
Gold: Wind of Chamon, Lore of Metal (and Alchemy)
Jade: Wind of Ghyran, Lore of Life
Celestial: Wind of Azyr, Lore of the Heavens
Grey: Wind of Ulgu, Lore of Shadows
Amethyst: Wind of Shyish, Lore of Death
Bright: Wind of Aqshy, Lore of Fire
Amber: Wind of Ghur, Lore of Beasts

(In addition there are non-colored magics, like necromancy, Skaven magic, etc.)

Magic has the classic Red, Green, Blue, White, and Black.

The DC universe has the various Lantern Corps, who really might as well be magical sometimes. (And Golden Age Green Lantern Alan Scott actually was a magic user, of sorts.)

I think using colors as an organizational scheme is one that works well for getting a good hook on things; you can tell the players, "So-and-so is a red mage, so watch out for blood magic and poor impulse control," or "She's a green mage and is protected by the spirits of the plains."

The other nice thing about the concept is its flexibility, as the OP demonstrates.

It also ties into something I've been thinking about lately; universal magic systems where everything and anything can be accomplished by the magic are good and all, but I'm finding myself more intrigued by limited magic, where some things simply aren't possible in magic - whether that's an ironclad law of the universe or just a lack of knowledge among the magical community. If some colors are impossible for humans to use, or using them carries a heavy price, I think it makes for some fun gameplay.