Most displays viewed in dark environments can easily cause dazzling glare and affect a viewer's dark adaptation state (night vision). In previous work we showed that legibility could be improved and dark adaptation preserved in low-light environments by using a display design with a specially selected spectral light emission. We used long-wavelength light (red) that is easily visible to daylight vision photoreceptors (cones) but almost invisible to night vision photoreceptors (rods). In this paper we conduct an experiment in which we show that negative polarity (bright text on a dark background) produces better performance in a legibility task than does positive polarity (dark text on a bright background). Our results can serve as a guidelines for designing displays that change their color scheme at low ambient light levels.