This paper deals with the origins of color aberrations (defects) that may occur in the beam patterns of projector lamps and ways to correct these. These optical aberrations cause the pronounced colored effect along the boundary of the cut-off line. Descriptions include basic analysis of the light beam superposition within the final light output and the influence of the shield position and shield shape to colored cut-off line effects. The forming of the light beam by the reflector, to a certain extent, determines which shield shape will be suitable for eliminating of the color effect. However the shield shape also correlates with the chosen lens. If the wrong shield is chosen than the color aberrations and other defects will arise. This paper describes basic principles that should enable the optical designers to avoid these effects.