What do you get when you combine a French orphan with a genetic defect and an isolated mountain region of Kentucky?
No, seriously. French orphan Martin Fugate was born with methemoglobinemia, an extremely rare genetic condition that caused his blood to absorb less oxygen than normal. As you may have guessed, this caused his skin to turn blue. The reduction in oxygen absorption was not serious enough to kill Martin or even cause any health problems, however... it just made him blue.
When Martin immigrated to the United States, he landed in a mountainous region of Kentucky. The geographic isolation of the area led to inbreeding, which, as you may have guessed, led to more blue children. Children carrying the defective gene continue to be born today.
Being blue left many of them, well... blue. To their delight, in the mid-1960s a doctor from the University of Kentucky Medical Center created a pill that temporarily counteracts the condition. If desired, the good people of Kentucky can now wake up blue but spend the day pink.
And you thought the grass was the only thing that was blue in Kentucky.