I have seen something of a similar nature to what ASalina has seen. I was in my room at one of the casinos in Las Vegas where there was a sticker on the mirror in the room which said something like this. "In the interest of the conservation of electricity could you please turn off all the room lights prior to leaving your room." The mirror was right near a window that looked out onto the Vegas strip. Now imagine the contrast of the sticker and the lights of Vegas through the window at night. I still laugh to myself when I remember that sticker.