Chaos Drives are those glowing tubes that come out of G.U.N. robots when you destroy them. They raise your Chao's stats by 24 for points (0.8 points on the Dreamcast). Chaos Drives are more popular because they don't affect the way your Chao looks, like animals do (i.e. no animal parts). To easily get Chaos Drives, play as Tails or Eggman because they fight more G.U.N. robots. There is a rumor about a blue Chaos Drive that raises all stats but this is NOT true.

Green -- Running
Yellow -- Swimming
Purple -- Flying
Red -- Power