Ok, mostly graphical stuff this time...
I think the grey-ish sea colour works perfectly, creating a great contrast against the colourful land areas.
On your latest image, you could increase the saturation of the land a bit, to give even more contrast against the nonplayable areas, but not too much - just make them a little brighter. Also, West Estonia could be somehwat lighter - blue numbers will probably be hard to see on such dark blue.
Then some other things... The impassables can still use some work. They don't seem to fit the map... seem a bit too pasted on.
The outer border around the playable land area seems unnecessarily thick. Also it doesn't seem to be consistent - on some places it looks more brown and blurry, others it's more black and thinner. A sharp, consistent border would look better. Kinda like the territory borders, but maybe a bit darker.
Also, the grid shouldn't go over the border lines. Put the layer with the grid under all the border layers. You could also try some other layer mode for the grid, to make it follow the colours around it - try multiply mode or something similar.