I had the same problem, and one complaint about this plugin is that it has no instructions. Login and select Font Settings in the middle of the top menu bar. A popup appears on the left with two “hands” Click on the large one, then select your block on the page. Another popup will appear and ask you to name the block. Do so, then select color and font. There shouldn’t be any add-on effect if you do it this way. If you try and select a previously-named block from the first popup, it doesn’t seem to apply the previously chosen fonts and colors. Also, the plugin seems to allow multiple blocks with the same name, but different fonts, which appears to be a bug.
If you’re still having problems, keep refreshing the page and dealing with the resulting popups until all the block outlines have disappeared.
