The random dragons come in different kinds, depending on your level. The first ones are just called 'Dragon', after that are Blood Dragons, then Frost Dragons, Elder Dragons, then Ancient Dragons. Some dragons have names, these dragons will be one of the types mentioned above.
The topaz dragons name is Fidelis. The ruby dragons name is Joyeu. The lapis lazuli dragons name is Fortuna. The emerald dragons name is Honora. The amythest dragons name is Veritas. The diamond dragons name is Forta. The opal dragons name is Hopian.
Well, it really depends on which dragons you're talking about. If you're talking about fictional dragons, then I don't have a single clue. However, if you're talking about real dragons, I'm your best source.