Method for approximating the spectrum of a plurality of color samples, the method including the procedures of measuring the color of a reference color sample in a color space, determining a reference sample estimated spectrum from the measured color, measuring the actual spectrum of the reference color sample, determining a spectral delta from the difference between the reference sample estimated spectrum and the actual spectrum, measuring the color of each of the color samples, for each of the color samples, determining a sample estimated spectrum from the measured color, and for each of the color samples, determining a sample approximated spectrum by adding the spectral delta to the respective sample estimated spectrum.