What is Blueish coloration of the skin?

Blueish coloration of the skin is called cyanosis. It is a medical sign that indicates a person's skin is not receiving enough oxygen. Blood normally carries oxygen to the body's tissues, giving skin a pink color. When blood is not properly oxygenated, it appears bluish. Depending on the severity of cyanosis, the skin may appear slightly bluish or deep purple. Cyanosis can be a symptom of a variety of underlying medical conditions that affect the heart, lungs, or blood vessels.