Select the color you want and click a country on the map. Right-click on it to remove its color or hide it. Advanced...
Hold Ctrl and move your mouse over the map to quickly color several countries/subdivisions. Holding Ctrl + Shift has the opposite result.
Add the title you want for the map's legend and choose a label for each color group. Change the color for all countries in a group by clicking on it.
: Zoom in/out
: Move Map
You can also use W,A,S,D,I,O on your keyboard or the controls on the right.
You can still change Fill Color, click on provinces to paint them, etc.