Why Does Cold Make Our Hands Blue?
Your hands appear blue when cold because the veins which are near the surface are filled with impure blood which is purplish in color. Your hands become cold because there is not sufficient circulation of warm red blood going on to keep them warm. The blood in circulating through your body sends warm red blood through the arteries, and this is returned to the heart through the lungs by way of the veins. The veins carry only used-up blood or what is left of the good red blood when the arteries are through with it. Its color is a purplish blue.
When your hands are blue it means that circulation of good red blood has practically stopped—the red blood is not flowing from the heart through the arteries in sufficient quantity and there is no color in the arteries, as the blood from the arteries has practically all gone into the veins. The veins are full to purplish blue blood, and this makes the hands look blue, because there are a great many veins in the hands close to the surface.