Strange that you should ask this, I was only think the same thing the other day.
The ones I know of (from my collection):
Blue: Strategy Strategy/Action Strategy/Simulation
Blue (Cyan): Driving
Blue (Dark): Pinball
Green: Adventure
Green (Light): Sports
Orange: Shooting
Pink: Family
Purple: Action
Red: Arcade
Yellow: Role Playing
Yellow (Dark?): Simulation
I hope this helps.