The screencap to the left is of a Twitter conversation between Mike Mearls and Jon Dilley that is particularly useful for some world-building I wanted to do with Krevborna, a setting where dragons are born from horrific instances of sin. As such, Mearls's mapping of dragons to the "seven deadly sins" is a good starting point for what kind of dragon would be created from which human sins, but it leaves some sins and some types of dragons in the Monster Manual still on the table. Since metallic dragons aren't actually good in Krevborna, we can throw them in the mix as well--but we'll need to move beyond the "deadly sins," which is fine because there are all sorts of sins one can get up to in Krevborna.
Rounding out the current list of dragons in the Monster Manual adds:
We can also expand the palette by including dragons from Kobold Press's Tome of Beasts: