In my games the Russians are Red, the Americans Green, the Germans Grey, the British brown and the Japanese dark yellow.
Perhaps you can lighten the japanese territory colors and darken their pieces to an amber color?
It’s just a suggestion. Many of us, I’m sure, are used to the Russians being red/reddish-brown.
Also, you can feel free to lower the topographical detail on the map if you wish. It’s neat, but if you think it might help with speed or something, then it’s not going to make me cry if you take it out. :P
And finally, any way you can put in an icon to list currently controlled territory values?