Our sun is nowhere near the temps that you have, but I persevere as I think any sun is better than no sun. Popeye always turned dark when I took him out. I think because it was territory unknown to him. Now he looks to go out, stays quite red and now stayed at the top of his outside viv instead of the bottom.
Its possible he is afraid. I take my boys out and my panther turns darker and freezes in to a statue, stays that way for hours. He is afraid of the birds and airplanes. My Jackson, however is totally fine, turns a beautiful color and just chills out.