The “man with blue skin” actually has argyria. He developed it by drinking a homemade brew of colloidal silver, believed by some to be a panacea. The silver permanently deposits around sweat glands giving the skin a blue-grey hue. There is no treatment for it, and it is as impressive in person as it is in the video.
Fortunately argyria is rare nowadays in part because of better regulation of silver-containing tonics. Blue patients do still sometimes walk into dermatology clinics, often to the dismay of the nursing staff who rush to get oxygen before they realize what the patient actually has.
I also had a purple patient recently, but that’s a story for another day.