Ireland (Celtic Rules)

Eire (OTL Ireland) remained mostly isolated for millennia resulting in genetic drift. Individual mutations led to localized population traits such as extra digits, bluish skin, violet or green eyes, and bright red hair etc shared by an entire isolated community. Such occurrences are far more rare near the coasts (especially port cities,) where the intermingling of heterogenus population groups is likely to occur.

Early Celtic Eire (map)

The History of Ireland - Wikipedia