I think it depends on what exactly you're doing, specifically what kind of tricks. A draft may be perfect, cold bloods tend to be a slower, calmer, some I've met are lazy. Hot bloods can be more reactive, but their also more responsive, so it really depends on personal preference. I think you should look for a horse that already has some experience trick riding and see what you find and see if you connect with that horse.
I think any color (other than something super light) would work with white in my mind I see tobiano.