The proud, noble reptilian clans known collectively as the Dragonborn tend to gather around the crags, cliffs, and canyons of Braelun, finding comfort in the overlooks (and easy takeoffs) such locales provide. This leads to frequent territorial overlap with the world’s dwarven populations, but the two races observe mutually beneficial accords that reach back centuries.
I’m going to kick things a bit old-school with these guys, and say that your scale coloration does determine your breath weapon, or vice versa. Chromatics only, no metallics or other funky dragon types. As an alternative to a breath weapon, a Dragonborn character may choose to have small wings, suitable for gliding short distances. Taking the wings increases mobility, obviously, but a winged Dragonborn will suffer certain dexterity penalties due to having to work around them in combat and in tight spaces. They only fold up so much.