false colour

noun
  1. colour used in a computer or photographic display to help in interpreting the image, as in the use of red to show high temperatures and blue to show low temperatures in an infrared image converter
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012