An optical system may include (1) a light-guide optical element formed from transparent material and having at least first and second mutually-parallel major external surfaces for supporting propagation of an image by internal reflection, and (2) a mediating layer adjacent at least one of the at least first and second mutually-parallel major external surfaces, the mediating layer configured such that (1) reflectivity, averaged over the visible spectrum, of light coupled into the LOE and transmitted between the at least first and second mutually-parallel major external surfaces at angles below the critical angle is higher than the reflectivity that would have been expected absent the mediating layer and (2) reflectivity of purely white light lies closer to a purely white color point for an angular range from angles below the critical angle to the critical angle than the reflectivity that would have been expected absent the mediating layer.