I can't say anythign about ages for them, but the color varies. The females are not necessarily less colorful than the males. The males I have are heavy on the blue with less yellow and some of the females are blue with yellow while others have been tan with blue. Some of the tan ones I've seen starting to go yellow but I couldn't say whether it's inevitable for them all.
Keep an eye on them, make sure they're eating, etc.
-----
2.3.0 uromastyx geyri (Saharan/Nigerian)
0.0.4 uromastyx hardwickii (Indian)
3.6.0 uromastyx macfadyeni (Somalian)
1.2.0 uromastyx ocellata (Sudanese)
1.3.0 uromastyx ornata (Ornate)
1.0.0 uromastyx benti pseudophilbyi