Face and tongue. Thermographic footage of a woman sticking her tongue out, showing her piercing. A thermogram shows variation in temperature on the surface of an object, measured by the long-wave infrared radiation it emits. The temperature scale is colour-coded from black (cold) through blue, green and yellow to red and white (hottest). This thermogram footage shows that the tongue is warmer than the lips, with the nose the coldest part of the face. The eyelashes are colder than the eyes. The round metal piercing is colder than the tongue.