java game - changing background color to black

Hello.
I’ve found free j2me game “Boulder Dash”(first 2 screenshots).
I’ve changed all graphic in the game(second 2 screenshots).

But I don’t know how to change the color of the bacground from white to black, so it would look likne on the last 2 screenshots.

Is there a simple way to do this?

Thanks.

http://members.chello.pl/g.kawiak/Boulder/Boulder.jpg

Normal game.
http://members.chello.pl/g.kawiak/Boulder/Boulder.jad
http://members.chello.pl/g.kawiak/Boulder/Boulder.jar

Modified game.
http://members.chello.pl/g.kawiak/Boulder/Boulder-Mod.jad
http://members.chello.pl/g.kawiak/Boulder/Boulder-Mod.jar