Polarization degree (left) and (g–r) color (right) images computed for a mixture of porous Halley-like particles (porosity 85%) and solid silicate particles (forsterite); the ratio of the constituents in the mixture is 9:1. The figure demonstrates the applicability of the rough spheroid model to modeling polarization and color for regular (not distant) comets. Polarization is given in percent and color in magnitudes, but are calculated for the white-light illumination, i.e. they represent the intrinsic color of the dust or, from the astronomical point of view, the dust color excess.