I'm partial to the idea that the djinn have bodies composed of dark colored glass with fire burning inside of them. This could give them a beautiful appearance that some of them are described as having as well as fulfilling the whole made of fire and sand bit (fire+sand=glass). It could also the different color theme that crops up. As for how this applies to the jann i'm not to sure. Glau is a huge pain in the backside for me personally at the moment. I really want to make a jann/djinn character that's somewhat close to what Mr. Butcher had in mind (im a purist that way >.<) and how the jann has been displayed in the books has kinda been bleh. Glau is ugly, frog like, has a stupid mouth with shark teeth, can run a little bit faster than normal, is kinda tough, and can maybe run on air. Oh, and he's a good lawyer..... a sharky lawyer(pun intended maybe?). Not that impressive for something thats supposed to be born for what essentially is the equivalent to an angel. Maybe I should bribe someone into asking Jim what he had in mind for them at one of his book signings... /sigh