If you’re not happy with the results of a drawing or coloring operation you can easily undo it by clicking on the pink half of the “eraser” that appears just above the color wheel (the gray half of the eraser pertains to the color mixers, see the Eraser for more details). Clicking the pink eraser multiple times undoes multiple operations.
To completely clear the drawing area in one step, click the clear button (the one that depicts a windshield wiper, see the Clear Button for details). When you clear the drawing area in this manner the current background color is retained. You can change the background by applying a new color anywhere in the blank drawing area.
You can achieve interesting results by drawing a pattern, coloring some or all of the regions and then erasing the pattern lines. Unfortunately, this can’t be done with the eraser because the eraser undoes drawing steps in reverse order. It can, however, be done by redrawing the pattern in the background color.