True dragons red, green, gold, etc.) all have innate spellcasting abilities. Other creatures of the dragon subtype may or may not depending on the creature and circumstances. A wyvern for example, would be a low int creature, barely smarter than most animals.
Dragons, are rare and powerful. In my game universe, they once had an empire that spanned many worlds (interperet that however you like). They view humans the same way most humans view kobolds or goblins. A threat if ignored, but sometimes you can negotiate with them.