I came across a crazy story about a rural Kentucky orphan name Martin Fugate, who, along with many generations of his descendants, it appears, had blue skin! The condition was due to a missing enzyme in his blood.
What was even crazier about this was that due inbreeding (not so much brother-sister as about 5 families continuing to refold similar genes into the same genetic pot), the recessive condition remained active for over a century. Even wilder than that was that by taking the proper supplement, the body could be oserved slowly changing from blue to pink! Searching the web will yield several versions of “The Blue People of Troublesome Creek,” a 1982 article that introduced the Fugate story to the world.