I add another idea to manage continent colors and also links between country.
We can use another svg as a background. It will include [colored shadow](http://www.w3schools.com/svg/svg_feoffset.asp) for each continent and links between countries like the [original board](http://commons.wikimedia.org/wiki/File:Risk_board.svg).
```Html
      <image xlink:href="board.svg" width="100%" height="100%" />
```