Your cham is dehydrated, a good dropping has one side black and the other side a pure white for a healty, well hydrated cham. A little yellow/orange is ok. Up the amount of time you mist. Do you have a dripper as well? What is your misting schedule?
You can also put your cham in the shower in his favorite plant. Place the shower head towards the wall so the pressure isn't too strong and will only mist him. This should encourage your cham to drink and will also rehydrate the skin as well somewhat.
What type of cham do you have?