A recessive gene and natural phenomenon.
You're probably thinking that that picture is a fake. Well, it's not. How did people get blue skin? Well, it's very rare, but you're about to find out.
This family, called the Fugates from Appalachia had blue skin (obviously). The Fugate family had a genetic condition called methemoglobinemia, which is a condition when too little oxygen is delivered to your cells. Then it passed through a recessive gene, and went throughout the whole family due to intermarriage. ABC News says that the Fugates probably had a deficiency in the enzyme called cytochrome-b5 methemoglobin reductase, which is responsible for recessive congenital methemoglobinemia. Bengamin Stacy, one of the more recent descendants lost his coloring and only when he gets angry or cold do his fingernails and lips turn blue. The end (of this particular article/story).
Cool!
Fascinating. I wonder if the genetic condition affects other parts of the body like the brain (thinking) or lungs (physical abilities). Thanks for sharing.