We developed a quantitative method for evaluating CEP(color expression power) in eye shadow. This method enables the cosmetic industry to measure CEP on an interval scales, so it is more accurate and reproducible than previous panel tests. Oil, colorants, Pigments and pearls are major factors affecting CEP in eye shadow formulas. We studied the oil effect on CEP using our unique method so CEP could be improved. We believe this method can be applied to other color cosmetics as well. In conclusion, we expected this method to be useful to formulator who want to improve the color expression power in color cosmetics. Additionally, we hope it will contribute toward developing the experiential know-how about color to scientific knowledge.