Hahaha that is awesome. No that isn't a good way to sex a panther and when they are that young it doesn't matter. I already had a male head bob at my other male that was 11 months old but not showing too much color at that point so don't let your chameleon be the judge lol.
Could you post some more pictures of your chameleon? I want to agree with Carol as it does look to be a male based off the tail. If you could take some more and get some good shoots of the base of the tail that would really help.