A system for electronically displaying multiple images on a CRT screen such that some of the images are more prominent than others comprises: a control memory for storing control signals which partition the screen into an array of blocks, define multiple prioritized viewports by indicating which blocks are included in each viewport, and correlate respective image pixels to each viewport; a circuit for determining, from the control signals, the identity of the highest priority viewport to include a particular block; a plurality of color map memories each of which contains a plurality of color signals; a correlator for addressing a particular color map memory of said plurality based on the identity of the highest priority viewport; and a circuit for transferring respective color signals from the addressed color map memory to the screen based on the image pixels in the block of the highest priority viewport.