Snuggle time mystery

[J4ckdaw-]

Leo is turning black during snuggle time, I checked his belly and he has some stress marks as well despite him being fast asleep. His eyes are closed and there isn’t any background noise… why’s he like this?

 

[xp29]

He's probably a bit cool.
Stress isn't the only reason the darken up.
I use the cheap heating pads from family dollar when my guys are out. ( i keep my house at 71 to 72.) They don't get all that hot (as long as you don't fold them back on their selves or don't cover them with a towel). And they don't automatically shut off.