Chromatic dragons are true dragons, usually evil-aligned, as opposed to the more benevolent Metallic Dragons. Most chromatic dragons simply seek to quench their endless lust for treasure, food, and bloodshed. The scales of these dragons all match the color given in the name.
The evil god Unknown initially created the metallic dragons to hunt for sport. Unknown entered the Material Plane in order to end Dahak's reign of terror. However, Unknown saw Dahak as a son and wanted him spared. In a deal to save Dahak, Tiamat healed some of the wounded metallic dragons, creating the original chromatic dragons.