A method and apparatus are set forth for modeling a coloring process in moving web manufacturing through dye response gain adaptation using measured sheet color spectrum; and dye response shape adaptation using measured color spectrum of the production sheet. The adaptation of colorant (dye) response gain uses the measured sheet color spectrum value at the value of maximum light absorbance of the dye. The adaptation of dye response spectrum uses the measured sheet color reflectance spectrum and sample sheet color spectrum with a corresponding response shape calculated using a formula to adapt the current sheet condition dye response shape using the dye response from the sample sheet on the assumption of a constant ratio of absorption change to dye concentration change.