sometimes yes....if they see you
lets just say you could make your chameleon go to sleep just by looking at them....
so you just made them go to sleep and you changed the way everything looks, then woke him up all without seeing you.... i doubt this would stress the cham out.
or it was awake the whole time and was in the cage while you were changing things. most likely if it is stressed out there are not so subtle phys. signs.
at any rate unless you are taking hrs to change things, even if it does stress out the cham not all stress is necessarily bad. Ive always thought small amounts of stress can benefit almost any animal.
without stress IMHO animals become weak in a way. chams stress in the wild lets not forget.
dont go overboard though.
a chameleon that passed due to stress related problems was either exposed to prolonged stress which make the immune system weak and fell victim to an illness, or was sick already and the stress did them in. depending on a lot of variables of course

its such a bummer to hear about cases like that betty, sometimes i feel like we are all exposing our chams to low levels of constant stress without even knowing it.