The Pencil tool also can be used as an eraser. If you select the Auto Erase option on the Options bar, the Pencil tool applies the Background color if the mouse cursor passes over pixels colored with the Foreground color. If the mouse cursor passes over any other color, the Pencil tool paints with the Foreground color. (For more information about the Foreground and Background colors and how to select them, turn to Chapter 5.)