In remote control systems (as in many other circumstances) the color representation of a bitmap is one of the heaviest factor in term of storage occupation and speed of transmission. Often, only a limited number of colors is actually used by a bitmap, so that the bit pattern of the single pixels is bigger than what is really needed to represent all the possible different colors.With the present invention, in case the number of colors does not exceed a predetermined thresholds, a palette table containing all the colors used in the bitmap is created. The pixel representations in the bitmap are then replaced by a pointer to the corresponding entry in the palette table. This allows to reduce the total size of the bitmap. The reduced bitmap is then transmitted together with the associated palette table. The receiving computer (the controller in a remote control system) is able to rebuild the original bitmap with the help of the palette table.