Final Fantasy VII/Magic Materia

The magic materia is green. Usually, it has 3 to 5 levels (stars), and each time the materia gains a level, it's possible to use a new spell, with the first being equivalent to slight tickling, the second being the one you use most, and third one being the one that kills everything dead (or heals everyone alive or something). There are a few exceptions like Ultima. The first star filled at the beginning and the last star being filled means the materia is mastered, thus depending on the stars the materia can usually have 2 to 4 spells - in Ultima's case, only one.