 The term countershading has a second meaning unrelated to " Thayer 's Law " . It is that the upper and undersides of animals such as sharks , and of some military aircraft , are different colours to match the different backgrounds when seen from above or from below . Here the camouflage consists of two surfaces , each with the simple function of providing concealment against a specific background , such as a bright water surface or the sky . The body of a shark or the fuselage of an aircraft is not gradated from light to dark to appear flat when seen from the side . The camouflage techniques used are the matching of background colour and pattern , and disruption of outlines . 
