A vehicle head up display system includes a transparent window assembly and an ultraviolet or infrared light source. The light source is used to irradiate transparent photovoltaic converters in the window assembly so that the photovoltaic converters produce an electric current. The electric current is transmitted to electrochromic pixels in the window assembly and actuates the electrochromic pixels in the window assembly to switch between having a transparent appearance and having an opaque appearance. Visual contrast between transparent pixels and opaque pixels provide indicia on the window assembly. The indicia can be removed from the window assembly by actuating the opaque pixels to have the transparent appearance by a subsequent application of electric current exceeding the threshold voltage. An electronic control unit can be including in the system for controlling operation of the light source.