Its color and attack pattern correspond with the element you are currently wielding, and changes its color if you switch to a different element.
Red = Fire
Blue = Ice
Yellow = Thunder
When it's red, it shoots flames from its right or left side (depending on which side of it Zero is on) like a flamethrower and then shoots a small fireball.
When it's blue, it shoots two snowflakes that rebound off surfaces.
When it's yellow, it shoots an electric blast wich has a short range but splits into two blasts when it is in the same vertical axis as Zero.
If Zero isn't wielding any of the three elements, it stays in the state it is currently in. Its default color is generally yellow.