I don't think this necessarily follows. The cells responsible for changing pigmentation might be able to react to nearby light wavelengths and match them, thereby camouflaging themselves to nearby objects. I think the idea that a creature would have to see the objects around them, process them all, view and appropriately assign all of its own body in a 360 degree view of how other being would be looking at it, and then consciously coordinating "OK, this part of me needs to be this shade of green, this part this other shade, this small spot brown, that part darker" and so on seems pretty far fetched, unless you're portraying the species as being some level of godlike super geniuses - which would then create the question of why they're using their incredibly abilities at multitasking and super fast information processing on just camouflaging themselves.