As a novel fan, I'll add that the skin colors change a lot, I always imagine them as being like a lava lamp almost. They also vary from social castes. Their bodies are supported by fluid filled sacks so their appendages can take on weird shapes and bend in unexpected ways. They are also often described as being impossibly beautiful, almost magical. They're basically Kif's species from Futurama with magical LoTR elf-like beauty. I think they're suppose to be quite a bit taller than most ST humanoids. They always evoke, to me, an image of the ocean.. like really colorful jellyfish or cephalopods. Their planet is often described with comparisons to coral reefs in the books as well.
