Natural sunlight is great and 86 is not too hot as long as he is not forced to stay at that temp the whole time. I mean he should have some shade to cool down if need be..
Is that the first time you have taken him outside? He might have saw something that he thought could be a predator to him. My cham gets very weird and skilly when he sees birds and planes flying overhead but he does not turn black.
They do go darker to absorb heat when outside - they seem to bask better outside! Real UV must feel wonderful to them! They also flatten their bodies away from the sun to increase the surface area of their bodies. If you create a shadow over part of the cham then the bit in the shade will lighten whilst the rest stays dark Here's a pic to show what can happen - I put a shadow over my first cham, Lily, whilst she was out in her sunbathing wire cage - the shadow of the wire showed lighter than the skin exposed to the sun. Anyway, I think the pic can explain better than I!!
him showing black could be either. you do have to watch the temps. even if you put his cage partial to the shade for him to retreat. dont rely on this.
i have a yemen that insist on basking no matter of the temps. it was close to 100 today. his cage is available to the sun only in the morning and evening. when i got home it was still very hot outside. it was about 5 and even with partial shade. he was out in the sun showing hot colors and gaping. so i blocked more of his cage and even with that effort he still went to the 1/4 of cage being in the sun.
how they live in the wild i have no clue. we must pamper to much in captivity they lose there wild intuitiveness.
I agree - my first female would sit and bask, go light and gape and STILL she would not move her fat backside out of the sun, even when she had plenty of shade! I would have to physically lift the cage and bring her back inside! They can be quite dippy sometimes!