Windows Paint 7 has several brushes that create interesting patterns. However, Paint has no masking tools so it can be tricky to fill in shapes without coloring outside the lines. The bottom shamrock was colored using this method (adapt it as wanted):
- Make a copy of the black & white outline (with Transparent selection) and just hold it on the clipboard.
- Choose a brush (I used the Natural Pencil brush), a line width, and a color.
- Draw, color, scribble your shamrock or clover with the selected brush. Change line widths, colors, and direction as desired. Don't worry about going outside the lines.
- Use the eraser tool to clean up the brush marks outside the lines.
- Paste the black & white outline on top of the colored image to restore the nice, black outline.
For more options available and to learn different drawing styles using Windows Paint 7, see this tutorial for drawing a Christmas tree.