Oh it's totally like cheating. I'm also playing a game as the Netherlands/Burgundy and was always wondering why France so totally trounced me whenever they got testy. And now I know. In my game as France though I destroyed Burgundy early on (like almost immediately, but they started it) and it got divided between me and Austria and now Austria is slapping me around some. It's humbling.

In that case I'd have to guess Portugal since they seem to be everywhere, and also they got the American colonies on both coasts which is what I like to do too.

Are you keeping all the indicated countries there? If so, doing colour variation for colonies could make the map even more complicated to read unless as you say you do a layer over the land. The difference between the yellows and the greens are very slight as it starts out.