Seal, thermogram. 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 and runs from purple (4 degrees Celsius, coldest) through blue, purple yellow to red (warmest, 24.9 degrees Celsius). This image illustrates how the blubber covering most of the body of a seal insulates it from the cold. Where the blubber is absent, (the eyes and the nostrils), heat loss is greatest.