We propose a colorization-based prediction algorithm, which reduces the correlation between luminance and chrominance planes, to achieve compact compression of color images. We first develop a priority-based colorization scheme, which adds chrominance values to gray pixels using a set of colored pixels, assuming that neighboring pixels with similar luminance values tend to have similar chrominance values as well. The colorization scheme assigns a high priority to a pixel that has a large number of neighbors with similar luminance values. Then, we employ the colorization scheme to predict the chrominance planes from the luminance plane. Since the priority-based colorization scheme predicts color data accurately even in complicated color regions, the prediction residuals can be efficiently compressed. Simulation results on rich color images show that the proposed algorithm yields better compression performance than H.264/AVC.