I want to raise a dark Speed/speed chao.

(Sorry I would change the unacceptable name in this post's title but I don't know how)

But my chao's speed stat has reached level 99.
Does this mean I can't make a speed/speed chao?
Or can I still make a speed/speed chao if I giving him green drives/animals?

You can still give him drives and animals to impact the appearance, yes.

Great! Thanks man.
Well, now I gotta give him a bunch of greenies to make up for all the purple drives I gave him. :>.>
Aww, man. I can't wait!