Magic Materia (N/A)
Command Materia (N/A)
Summoning Materia (N/A)
Independent Materia (N/A)
Support Materia (N/A)
Green Materia is the actual Magic of the game. Like Fire, Ice, and Bolt. Yellow Materia is the Command materia. This materia adds abilities to your character such as: Steal, Slash-All, and Deathblow.
Red Materia is the Summoning materia. This materia calls powerful beings to your defense such as Shiva, Ifrit, and Ramuh.
Purple Materia is the Independent materia. This materia usually brings up your Characters status like luck, with such spells as: Chocobo Lure, Cover and Enemy Lure.
Blue Materia is the Support materia. This materia 'helps' other materia by giving it extra abilities like Added Effect, Sneak Attack, and Counter. It could be very very handy!!! =)