Polarization color ratios P_B∕P_V (left panel) and P_R∕P_I (right panel) as functions of α. Earthshine data are indicated by filled symbols. Blue left half-moon symbols indicate the Pacific side and green right half-moon symbols the Atlantic side. Values derived from Moonshine spectra are indicated by nonfilled (open) symbols for the respective sides of the Moon from which the moonlight is scattered. Models of Stam (2008) are overplotted with different linestyles. Values derived from model spectra of Emde et al. (2017) are indicated by stars.