Traditionally, single constant Kubelka-Munktype colorant formulation algorithms have been used for color control in the paper industry. One of the limitations of the Kubelka-Munk approaches is that they neglect fluorescence phenomena and the interdependence of absorption and scattering. In this article, an extended phenomenologic model is derived, incorporating fluorescence and interdependence of absorption and scattering. This model predicts illuminator-independent radiance transfer factors based on dye-on-fiber, from which the total radiance factor responses under arbitrary illumination can be computed. Illuminator-independent responses to changes in colorant concentration can also be modeled, allowing control of illuminator metamerism in coloring processes with fluorescent colorants. This method requires spectrofluorinietric (two-monochromator method) measurements to characterize the coloring process.