You have to be careful when using the Fill Tool for this reason: if you click in an unbounded area of the icon,
the color will "spill" out and fill more of the icon than you originally bargained for, possibly obliterating parts
of the icon that you wanted to save.
Look closely before applying the Fill Tool to an area to make sure it is bounded on all sides and that no "paint"
can "seep out" and get where it's not supposed to go. If this happens by accident sometime, don't panic. Just
Undo the Fill tool, find the "leak" and close it with the pencil or line tool, and then re-apply the Fill.
In this example, the Fill Tool used to fill in the the different regions in this abstract composition with