The physical process of color formation is described and an effective model is built for materials’ optical properties simulation and color prediction. By means of density functional theory, the complex refractive index of wurtzite ZnO is calculated and the results are consistent with the experimental results. Based on the calculation and analysis of the reflectance spectrum of ZnO thin films, predicts that the color of ZnO thin films are tend to be yellow, also in line with the actual sample. The effect of film thickness on ZnO color is studied. The results show that the thickness of ZnO film at the coherence length range (<1 300 nm) has a significant impact on the color modulation, and the color and brightness are tend to be stable when the film is thick enough (>1 300 nm).