This paper concerns the effects of Cl/F ratio, stoichiometry, incorporation of Mn, Sb, and Cd, and of thermal treatment on the formation of color centers in calcium halophosphates. Short wavelength u.v. radiation, or the discharge from a Tesla coil, induces three color centers in the 2500–7000Aå region. The spectral distributions of these centers depend on the Cl/F ratio. Incorporation of Sb and Cd and/or rapid quenching of the samples from elevated temperatures leads to a decrease in induced color center formation.