Pale lips are caused by a decrease at the surface of the skin or mucous membranes. Oxyhaemoglobins are red blood cells which give the lips their red color. With the absence of Oxyhaemoglobin, the lips will look pale and not the typical red color. Pallor of the lips could be an indication of minor to serious conditions. For more information, go to http://www.ask.com/wiki/Pallor.