Now, I understand there are some things to consider about this suggestion like that there are some colors used way more than others and that people might try to exploit this by switching to the winning color during an event but I have yet to think of a way to override this like make up a ratio of how much a win with X color means compared to a win by Y color or only award players who contributed to at least 2-3% of total land acquired. I dunno, I guess this would need to be worked on further.
I also dont know what the limitations to implement this would be in a Flash Player environment, I admit I'm not very knowleageble of this software so dunno how it would keep track of who wins or loses to update the map (I would suggest by color of cards in a deck, this way people who multisphere will usually have more of a color then another in it).
So that is about the gist of my suggestion, feel free to add improvements if you like it or constructive criticism as well (or you can just say it's horrible I won't take it too hard
Cheers!

