You can insert a line by clicking on the - symbol in the toolbar.

This is the code for a line:   <HR>

This is the code for a line on color: <HR  color=ff00cc>

Colors are designated by a combination of 6 letters and numbers.  If you click on the big A in your toolbar, the color chart will drop down.  If you hold your mouse still over a color, the code will show up.