Raynaud's phenomenon (RP) is a condition resulting in a particular series of discolorations of the fingers and/or the toes after exposure to changes in temperature (cold or hot) or emotional events. Skin discoloration occurs because an abnormal spasm of the blood vessels causes a diminished blood supply to the local tissues. Initially, the digit(s) involved turn white because of the diminished blood supply. The digit(s) then turn blue because of prolonged lack of oxygen. Finally, the blood vessels reopen, causing a local "flushing" phenomenon, which turns the digit(s) red. This three-phase color sequence (white to blue to red), most often upon exposure to cold temperature, is characteristic of RP
My friend has this, and she says it's because she has trouble heating up her hands and feet. They get cold, and turn reddy purple. I think it has something to do with the blood.