How do you cure cyanosis?

Cyanosis is not a disease to be cured. It's simply a change in skin tone to bluish hue, mostly observed on finger nails or lips; caused due to insufficient supply of oxygen that causes un-oxidation of haemoglobin within blood. Hence the underlying health cause should be treated appropriately by trained medical professions and depending on the diagnosis; it's likely cyanosis would disappear naturally.