so how friendly are most chams. my little geb absolutely adores to be out and about with everyone. He even enjoys piggy backing on the family golden retriver. how common is it to have an extroverted cham???
So, describe for me how you know he "absolutely adores to be out and about with everyone"? How do you know he enjoys riding on your dog? The reason I ask is that you could unintentionally misinterpret his responses to these sorts of things. People often assume that bright colors are a sign of happiness and enjoyment. Not necessarily! Sure some chams are more tolerant than others and that's great. But you can definitely misread him.
Color change is a response to stress. As a cham gets more and more stimulated by activity the stress hormones fire off more and more. And the way a cham communicates its stress level is through color change as well as body posture. Not ALL stress is bad, but too much can be over time. What I mean is that your cham registers mild stress (such as getting excited over hunting food, getting out of the cage to roam free, being picked up) with some color brightening, but if the stress keeps on rising, his color eventually shows that he's defensive, afraid, angry, territorial, or shocked.
It could be he is pretty upset by riding on a very large hairy animal that could well be a predator...after all he doesn't understand how benign your dog is. He would normally show some color brightening when he's being handled and much of this can be OK. As you get to know his moods you'll soon learn when he's telling you he's passed from mildly excited to alarmed and "had enough!".
Just don't assume he loves what you subject him to. Consider how he is probably thinking about it and why. The dog is an unknown animal. Could hurt him, eat him, or ignore him. He's going to assume the worst at first. Let him.