The fingernail beds are a highly vascular part of the body and as a result typically have a pinkish tone reflecting the normal reddish color of blood in the capillary beds beneath them. When a person's hands are cool, it is possible for these blood vessels to constrict, causing the nails to become more pale or even take on a bluish hue. In addition, when a person is not getting enough oxygen delivery through the blood it is also possible for highly vascular areas like the fingernails, fingertips, or lips to take on a bluish hue. In order to determine what might be causing your symptoms, it will be important to see your physician right away. He or she will want to examine your hands as well as take a more thorough history to find out if you have noticed any other changes. Depending upon your age and prior health issues, you may also be at higher risk for certain conditions that can lead to vascular constriction in your hands. Without any chronic lung problems and in the absence of any shortness of breath or trouble breathing recently, it is very unlikely that you are having problems with oxygenation, but it will be important for your physician to do a thorough exam to make sure this issue is diagnosed and managed properly. Hopefully your hands will be back to their normal color very soon!