Very normal. Remember they are cold blooded animals and do not generate their own body heat like we do. Also, our body temp is around 98.6 degrees, so touching an animal whose body temp is around 75-80 feels cool to us. Get a glass of water that is about 80 degrees and put your hand in it. It won't feel cold, but will feel cool.
Just kidding, obviously. LPSouth is spot on - feeling cool to the touch is totally normal. The only time my Jax is "warm" to the touch is when he has been basking and climbs straight on to my hand. Otherwise, he is pleasantly cool but not cold, particularly on the belly.
FYI, chameleons hate having their fat little bellies poked.