Native to the Navir Isles, of which Ganao is the main city, the dragonborn are seen in almost every colour except for silver and white. Their different breath weapons and resistances make them useful for almost any situation on the tropical islands.
Nobody really knows where dragonborn come from, and they are a somewhat recently discovered race, but their numbers are rapidly increasing as they have been migrating a lot recently.
The dragonborn elders are keeping their origins under wraps and plan to die with this information leaving none of the younger dragonborn with it. The reason for this is unknown except to the few elder dragonborn who haven't died yet.
There are just a few of each colour left alive, and elders as they are, their word is law. They are, however, also beginning to go senile, grow sick, die off, or getting more and more frustrated with being kept safe and alive through whatever means by their descendants. This has even made Vyrph the Old attempt suicide much to the discontent of her caretakers, guards, extra guards, children, and grand children, who now watch her at all times.
The Rimnos Invasion
No one knows where they came from. The cold dragonborn, or The White Death, arrived at the shores of Rimnos one day, where the stories tell that they were met with hostility and thus they took the city by force due to their icy breath weapon, cold resistance, and powerful yet agile build rivalling the Tabaxi.
This was many hundred years ago, and they make up a good 30% of the Rimnos population today, just as docile as their cousins on the Navir islands, though both the Naviri and the Rimnonese dragonborn deny being related in any way.
Thus nobody really knows where these cold dragonborn came from, but they can now be found in any major town or city in the north.