The effect of the concentration of a colorant (masterbatch) and the surface texture on the color of an opaque injection-molded plaque is experimentally described by means of the spectral reflectance and the CIELAB coordinates. It was noted that the surface texture had a marked influence on the experimental results and on the perceived color. The relation between the color of these pigmented plastic plaques and intrinsic physical material properties, such as light absorption and scattering coefficients. is described by means of the Kubelka-Munk equation for pigment/ paste mixtures. The concentration dependence of this Kubelka-Munk equation for different masterbatch-polymer mixtures can be modeled in terms of the color of the individual constituents using a fitting parameter. Further experiments were carried out which indicated that the fitting parameter had a physical meaning. The effect of the surface texture on the optical appearance of the plaques can also be accounted for by this parameter.