Couple kissing. Thermogram of a man and woman kissing. The image shows variation in temperature. The temperature scale runs from red (warmest) through yellow, green, cyan and blue to mauve (coldest). Thermography is a technique for visualising the temperature of surfaces by recording their emission of long-wavelength infrared radiation. This heat radiation is detected electronically and displayed with different colours representing different temperatures. In this case the temperature variations on the surface of the skin are shown.