There seems to be a fundamental misunderstanding here of the anatomy, physiology and purpose of a chameleon’s so-called ability to blend in with it’s surroundings.
A lot of chameleon color display has to do with threat and territoriality. A male veiled chameleon, for example, ripples with gorgeous colors when faced with another male encroaching on its territory.
Most of the rest of the time, it’s green. Sometimes when it is out of the canopy, on, say, bark, it will turn brown. That’s about it. Sorry.