The following is a simple painting program. It uses Windows Forms and will allow you to draw whatever you want.
You can also include code to change the colour or size of the brush via a right click menu by using code such as this:
MenuItem mi = new MenuItem("Option");
mi.Click += new EventHandler(mi_Option);
cm.MenuItems.Add(mi);
void mi_Option(object sender, EventArgs e)
{
// code to change colour, size etc.
}
There are bugs with this, if you quickly move the mouse around the lines are not solid. This is because the program is basically drawing multiple circles on the form. Still, it's simple and can be improved upon.
Lots of Google help went into this, so credit goes out to the developers better than myself :)