Runners

If i would colour it, I would give it stripes and green-like skin.
It depends on how they're couloured, that they can run fast for a long time extremely fast for for a short time.
If they can only run very fast for a short time,like a cheetah, i would give them, as listed up, a skin that can blend in its surroundings, so that he can stalk its prey, until they're close enough, and then be sure to catch it.
And, for taking down larger prey, you can say they have, like raptors, a big claw on their hind legs, and by jumping(on the drawing he seems like beeing able to jump very high) on a large creatures back, beiing able to kill it.
Very cool design, btw!