Cyanosis is a purplish-blue color of the skin. Newborns with cyanosis are often called blue babies. Cyanosis means that there is less oxygen being carried by the body’s blood cells. In this situation, there may not be enough oxygen being carried to the tissues in the body. The colour is caused by high levels of reduced (deoxygenated) hemoglobin in the blood near the surface of the skin. Hemoglobin is the molecule that allows red blood cells to carry oxygen. Oxygenated hemoglobin is bright red, while deoxygenated hemoglobin is bluish. There are two main categories of cyanosis: central and peripheral. Central cyanosis causes a bluish colour in the lips, tongue, and skin, especially the fingers and toes. Peripheral cyanosis is seen only in the fingers and toes. Cyanosis caused by congenital heart conditions is often seen soon after birth, but sometimes it does not appear until a baby is older.