I've found that the orange markings on baby collareds can remain anywhere from 2 months to 8 months. Male collareds generally have brighter markings that last longer than females. Which has, I'm sure, confused many people when purchasing young collareds as people, including me, figured that the ones with the stronger orange markings would be female. This can obviously vary between sub-species.
As far has your collareds turning green and yellow. Well, this depends again on the sub-species and the actual lizard. Some collareds will turn bright blue (bluestars), others turn a nice blue/green with yellow combinations (aquaflames), most will have mostly yellow markings around their head, feet and tail. No matter what sub-species you should start to see colouring around the 6-8 month range with full colouring not present until 12-18 months.
Collared Lizard Images