I would guess by the response that nobody has any idea? I have never seen this done, and it really serves little to no practical purpose. If its to tell what dragon is what I would question why they are being housed together. As far as the male to female this isn't hard to determine if its an adult. If its a hatching or juvenile then sexing is an educated guess at best. What was the reason for the question? also this probably varies depending on who is marking them. Probably best to just ask someone where you have seen them with markings. You could also consider using a label on the enclosure.