i agree with Jefe you would ruin the look of the game. The black and white the way it is now is classic. you can't throw it all away!
I made a suggestion once for this: http://community.freeriderhd.com/threads/night-time-mode.1671/ Some people took it to mean inverted colors, but I think just a less harsh white or not such strong contrast between the colors would be preferable to help with eye strain.