So I bought two full grown uromastyx at a recent reptile show so I could have some companionship in my apartment, and I decided to name them Tori and Kari (yes, named after Mythbusters). The darker one is Tori, and once I get a shot of his back, you can see that his back is bright yellow. Being a female, Kari is more bland in color. But that's the way nature tends to go :).