A family from US had blue-coloured skin
The Fugate family from Kentucky, US, is believed to have had blue-coloured skin, due to a condition called methemoglobinemia. It was caused by a type of haemoglobin that couldn't carry oxygen through blood, making the skin look blue. The first generation developed the condition around the 1820s, but the treatment for the same was first performed during the 1960s.