You don't want to use any of the red or blue bulbs (or any "bulb" really) at night. If you're enclosure gets too cold at night you can use a ceramic heat emitter, but be very, very careful with them! Your chameleon won't recognize its there and can basically cook overnight if the heat emitter is too close to it. You're ususally better off leaving no heat source at night as most need a temp. drop at night to be at their best.