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