An algorithm has been developed, using the subtractive primaries, that enables a ‘synthetic reflectance curve’ to be calculated for any set of XYZ values. A wide range of reflectance data for cyan, magenta and yellow primaries and white substrate can be used as data for the algorithm, provided the curves are smooth and correspond to those colours. These synthetic reflectance curves can be used as replacements for the data from measured physical standards for match prediction purposes. The synthetic standards have good colour constancy under a range of illuminants. They have been used to speed up the generation of fashion shade ranges selected initially on a CAD system.