For all of you out there that obsess over side character names, it looks like the red dragon had an actual canon, at least within the studio. Nayuki on the Allspark Forums (A layout artist from the FiM Team) states that he was called Garble in the actual script.
The only one of the teenage dragons who got a name in the script to my knowledge was the red one. Garble. I kinda feel bad about posting this though... the fans love coming up with their own names for characters after all. But yeah, Crackle and Garble were the named dragons from the episode. - Source NayukiSo there you have it! Better go edit those fanfics in progress!
The other dragons still remain unnamed, so go nuts with them.