they are in the average a little taller than humans, the moderate shape shifting lets them make a small formation of precious stone around them to hide or other purposes (a shield or weapon if they are desperate) and they can change their colors as a sort of camuflage. They can create light from their gems (kinda like a flashlight) but they have to focus and doing it too much gives them headaches, they have furry wings and are capable of flying, they are wise but they are not the smartest of the bunch (say -2 Int, +2 wis), and they have hollow bones(like birds)
Looks: They have different colors from all over the rainbow and beyond but they usually have a single color scheme (say if he can several shades of yellow but not like yellow with blue stripes), they have light fur designed to help them fly and keep them cold in Hot climates (this also make them react badly to cold), their faces are a little flat and long, and their ears very round and big but the fur mostly covers so they won't look weird, aside from that they are mostly human looking.
- face can appear darker/lighter and on different colors. (and like monkeys they have no fur in their faces)
- the reason they don't just use weapon/armor out of gems or mine them for trade is because they are part of their body and can be absorbed back, the stone (say diamond) are a lot harder that skin but they also feel as much (maybe even more) pain that their regular skin even if they can just make more and it would be as cruel as chopping down the arms of trolls just because they can grow them back.