my old grayscale SONY Clié T415 had a "hack" script you could enter which would invert the backlight, giving "white" text on a "black" background. this ability seemed to be limited to grayscale and b&w screens only. trying the same script on a color screen device wouldn't yield the desired result, but the "inverting backlight" notice would still display, so it seemed to want to work.
perhaps an application could be developed for the 'berry, which would do the same, or perhaps recode the LCD's color palette to swap out some hues. perhaps red text on black for "night vision" or something akin to Indiglo.