As we know, color appearances of a color patch are usually affected by its background or spatial frequency. The study intends to explore the perception as the patches are placed on different achromatic backgrounds, and the assimilation as the spatial frequency of patches is changed. We design two graphical user interfaces which are implemented by MATLAB R2007a for assisting the experiments. The results of this study find: the lightness of backgrounds can affect the lightness and saturation of central patches, and the patches tend to assimilate another color when the spatial frequency is increased. We expect this study will be helpful to predict more complex color phenomena and establish more advanced color appearance model in the future.