The Yellow Chaos Drive(Also known to fans as the "Thunder Drive") increases stat points in Swimming(Defense in Chao Karate). This will help your chao win swimming races alot. Collect lots of em'!
This one is really cool! The Purple Drive increases your chao's flying ability(Notice the child chao's tiny pink wings)! Flying will extend your reach of glding down in a race, and if you put your chao up on a high object, it may jump off and start flying! Flying is cool, so collect tons of Purple Drives!
The Green Drive increases status in the Running trait. If enough drives are givin, on the second evolution(See "Chao Evolution" page), it will become a Sonic Chao! Green Drives help a chao in running, which counts for all races(Running is Speed, to hit the opponet faster in Karate)!
The Red Drive increases status in the Power Trait. Power is climbing basically. It's a MUST in Chao Racing. Though, in Karate it acually is power, not something wierd like crawling and such. Power is also a MUST in Chao Karate. It allows you to hit your enimies much harder than usual. You know, I wish I had one of those...
For more ways to increase stats, visit the "Small Animals" Page, and the "Chao Kindergarten" Page.
Let me be blunt: There is NO Blue Drive or any such thing as that! The only Chaos Drives are the ones mentioned above!