You say your cham likes the incense... Therefore I assume he is exposed to it... and that is not good. I am paranoid sometimes, and overly cautious, but this just doesn't sound good. The fact that he changes colors to these enviromental changes would worry me even more. That means that these things, neither of which are natural occurances for them, are having some kind of effect on them... And I would be willing to bet the color change is more stress related, not trying to be a jerk, But music and air quality are 2 things that can easily stress out a cham. Often times we humans like to think of our Chams as little people in Cham bodies... what may appear to us as "aww they like it" could mean the exact opposite. Trust me... This won't be the only sacrifice to be made for your chams...
Respectfully,
~Joe