Raynaud's phenomenon is a vasospastic disorder causing discoloration of the fingers, toes, and occasionally other extremities. This condition can also cause nails to become brittle with longitudinal ridges. The cause of the phenomenon is believed to be the result of vasospasms that decrease blood supply to the respective regions. Emotional stress and cold are classic triggers of the phenomenon, and the discoloration follows a characteristic pattern in time: white, blue and red.
For more information, please see http://en.wikipedia.org/wiki/Raynaud%27s_phenomenon
Raynaud Phenomenon – – Raynaud's & Scleroderma Association – http://www.raynauds.org.uk/raynauds/raynauds