A monochrome display is converted into a color display by including an electrically controllable planar color filter plate switchable between primary colors and operating the display in a color field sequential mode. Hence the requirement for a color switchable illumination source is eliminated. For example the illumination source may be a white OLED, an illumination type which, in combination with a microlens array, has proven well suited for directional displays. Further the need for a color mask is eliminated, thereby eliminating problems of moiree interference with a microlens array and further eliminating problems of diffraction patterns in infrared images captured through the display for example for observer tracking purposes. The electrically controllable planar color filter plate may comprise two wavelength dependent wave retarders and two liquid crystal cells.