A display device comprises a substrate which carries an array of pixels. Each pixel comprises an array of apertures in the substrate, each aperture of the array having a maximum opening dimension less than the wavelength of the light to be transmitted through the aperture. The effective dielectric constant of the aperture and/or the dielectric constant of the substrate is varied, thereby to vary the light transmission characteristics of the pixel between transmission of at least one frequency in the visible spectrum and transmission of substantially no frequency in the visible spectrum.