This document specifies the method of calculating colour differences according to the CIEDE2000 formula. This document is applicable to input values of CIELAB L*, a*, b* coordinates calculated according to ISO/CIE 11664-4. It can be used for the specification of the colour difference between two colour stimuli perceived as belonging to reflecting or transmitting objects. This includes displays if they are being used to simulate reflecting or transmitting objects and if the tristimulus values representing the stimuli are appropriately normalized. This document does not apply to colour stimuli perceived as belonging to areas that appear to be emitting light as primary light sources or that appear to be specularly reflecting such light.