Donna,

I don't see anything major wrong with your husbandry at first. When you say stressed, is it just his color or his behavior also? Do you have a photo? He may be feeling his teenage hormones if he's around 6 to 8 months old. That is also when his adult coloration is getting defined. You may have already thought of this, but can he see his reflection anywhere around the cage? Can he see other animals?

It is possible that moving him outdoors often is keeping him unsure where his territory actually is.