How to determine pure-bred Gouldii monitors?
 

I have a hypothetical question to ask all of you.

Lets say I found a baby monitor offered for sale advertised as a sand goanna/gouldi/flavi/etc etc etc. Is there any way to check and see if it is in fact a pure bred gouldi/flavi and NOT a mislabeled argus/gouldi hybrid, or just a regular argus?

Again, this is hypothetical, and I'm not looking into getting a monitor right now. This is for future reference.

Thank you!