Go into the scenario/apolyton/default/gamedata directory open the file Colors00.txt and edit the following line COLORSET_COLOR 215 215 215 # COLOR_PLAYER1
The three values are Read Green Blue so if you want blue change it to:
COLORSET_COLOR 0 0 215 # COLOR_PLAYER1
I would however sugest that you use another color as blue is the color of the ocean, so you cannot se yourself on the radar map. Personally I use the color 155 155 155 a dark gray, visible both on the radar map and in the variouse screens.
Martin the Dane