its a shame they can't (their vision is bad and they probably can't see colour anyhow, only light/dark). But the pics that I have seen of your scorpions, they match their backgrounds so perfectly. Its quite amazing. Its almost like they can see light/dark and they're able to match it, hence their almost perfect camouflage into the substrate.
But no, I've not heard of any species of scorpion that can alter their coloration, unfortunately!