RoughCoronet0
Dragon Lover
I recall both Metallic and Chromatics were subjected to the transformations into Catastrophic Dragons. I definitely remember that the Wildfire Dragons in particular were once Red and Gold Dragons.They're more like Dragons of the Elemental Chaos, but in 5e with the elements being just as much related to the Prime Material as they are to the Inner Planes, I could totally see Primal Dragonborn. I just think if you're going to do Catastrophic Dragons, the Chromatics sort of move into the Prime Material space, while if you don't do Catastrophics, the Chromatics play up more of their Elemental Natures.
You may notice on that list a few Elemental Dragons that aren't Catastrophic Dragons. That's because they're Chromatics that have become more Elemental due to exposure to one of the Inner Planes / Elemental Chaos, and become Elementals Dragons instead of Natural Dragons (to use 4e parlance of Origin Type + Monster Type rather than conflating the two like 5E does).
Grant it, it always made more sense to me that the classifications of Chromatic and Metallic Dragons didn't really exist until after Tiamat and Bahamut came into being to create such a divide, so technically Catastrophic Dragons were never actually Metallic or Chromatic to start.
I also classify them as Primordial Dragons in my world.