I have found that by changing the first series of numbers in the PAL.CFG
file, I can change the background color of the game board:


The three sets of numbers represent (from left to right) the three basic
 colors: red, green, blue; and changing these numbers results in different
 hues and shades of color.  To have less red, for example, reduce the
 first number toward zero.  To have more blue, increase the last number in
 the series.

The default background color for the game board is tan.

To get a blue background, change the first three numbers to: 0 23 33

To get a green background, change the first three numbers to: 0 33 23

By playing around with the different mixtures of the three colors, you can
 design a game board (or any screen) with the colors you find please you
 most.