Abstract: "The electron paramagnetic resonance (EPR) of color centers in additively colored KCl crystals is measured to observe the effects of optical bleaching at room temperature. Earlier measurements on the F-center are confirmed and the susceptibility is measured at 78 and 300 deg K over five decades of power, including the very low power region. The width and the saturation properties of the individual multiplets are studied in detail and the technique of making EPR measurements on inhomogeneously broadened lines is discussed. A calculation is presented which shows that a slight departure from a Lorentzian multiplet shape can account for the saturation data. The bleached crystals show a resonance which has a width of 35 gauss and a different rate of saturation than the F- center. This resonance is associated with the B-band which appears in the optical absorption."