I'm not sure if I'm missing something in the question, but SVG plays very nicely with CSS. I frequently download SVG map files from Wikipedia, add new, more suitable, IDs to the relevant <path> elements, and then add a CSS section at the top for shading individual countries or regions or whatever.
The complex part is usually simply working out which country/region/whatever corresponds to which <path> in the first place; but this is a complaint more about the quality of the markup of the underlying SVG of an average map on Wikipedia, than about SVG itself.