Dear AMA,
There are some rare hemoglobin (the part of the red blood cell that carries oxygen) abnormalities that can cause skin discoloration. There are also many different dermatological abnormalities that can lead to red-purple skin. Most cardiac conditions (e.g. heart failure, congenital heart disease) that can lead to skin discoloration are easily diagnosed with physical exam and echo and not generally missed. If this is bothering him I would probably start by seeing a dermatologist.