sentences:  To reduce the image degradation by reflection of ambient light, contrast can be increased by several methods.In addition to black masking of unused areas of screen, the phosphor particles in color screens are coated with pigments of matching color.For example, the red phosphors are coated with ferric oxide (replacing earlier Cd(S,Se) due to cadmium toxicity), blue phosphors can be coated with marine blue (CoO·"n") or ultramarine ().