Yimir has a rather different ecology than the standard Pathfinder setting, so the races are changed accordingly.
Non-playable Grey Elves
Draconic Bloodlines Each of these races have been, at some point, interbred with polymorphed dragons. Humans and wood elves are most likely to have mixed blood. Wood Elves typically have Green dragon blood, and humans either have black or white, depending on whether they live in Oslund or the Northern Wastes. Red dragons interbred rarely with mortals, viewing it as beneath them, although they occasionally mate with mortals they view to be ‘exceptional.’ Your character may possess such a bloodline, but it is not mandatory, and will cause certain personality propensities.