Dark- stress usually made by high traffic area's where there is too many humans commuting, eye contact with another chameleon etc.
Pale with mouth open- overheated get a lower wattage bulb, and mist more often
Bright coloring when exposed to another chameleon- Normally this is only so with the males if they are puffed up and very bright it means they are threatened by another chameleon or by you, females usually just turn dark when exposed to other chameleons unless she wants to mate, in that case she will be very bright pink (receptive) or very dark(unreceptive)
thanks! Lucy was really dark when i got home yesterday and i realized i had not turned her heat lamp high enough. i turned it up to high to heat uup her cage and pulled her out. she grabbed my finger and wraped her legs around it and seemed to go to sleep. her color went lighter almost as soon as i started holding her. im guessing she was cold and was happy my hand was warm?