In this paper, we look into the superposition of two periodic clustered-dot color halftones, which are widely used for electrophotographic printers due to their print stability. The scope of our research lies in understanding how to make the best color assignments to the two regular or irregular halftones in order to minimize the perceived error. We develop a model that agrees with a human observer and allows fast implementation. In order to account for the difference in the responses of the human viewer to luminance and chrominance information, we use the Y_y C_x C_z color space, which is a linearized version of the L*a*b* uniform color space. The perceived error helps us identify the configuration of colors and screens that will improve the appearance of the superposition image. We believe that making the right color assignments is essential for developing high quality color images.