A backlit display sign includes a rear sign enclosure element at the back of the sign with a forwardly facing wide mouth opening. Extending across the mouth opening is a front sign element or cover formed from an optically transmissive light guide which extends laterally across the mouth opening of the display. Light diffusing (scattering) reflective layers on the front and rear surfaces of the guide or within the guide itself make the guide a light propagation sustaining channel that serves to funnel light rays laterally and forwardly within itself to an image-producing opening where the light is allowed to be emitted for producing the image of a symbol, letter, number or other indicia that is visible on the front of the display. A light cavity between the front cover and the rear sign enclosure element contains at least one illuminating device, e.g. a light emitting diode (LED), to provide visible illumination that is transmitted from within the light cavity through the guide to the front of the sign. A light reflective layer is provided on the inner surface of the rear sign enclosure to direct rays forwardly. A light tunnel can be supported within the sign to furnish light of a selected color from a second light source within the tunnel to a portion of the sign within the bounds of the light tunnel where the different color is provided than that of the illuminating device used for the rest of the sign.