This study investigates the impact of light and dark display modes on usability in mobile cartography. While display polarity has been widely examined in text-based interfaces, empirical evidence concerning map-based tasks on mobile devices remains limited. Using a split-plot experimental design (n = 35), participants completed map overview and recall tasks in both light and dark modes under self-reported bright and dark ambient lighting conditions. Results show no statistically significant differences in overall task performance between modes and lighting conditions. Dark mode yielded marginally higher scores for overview tasks, whereas light mode showed slightly higher recall performance. These findings suggest that dark mode maps can offer usability comparable to light mode maps, supporting their adoption in energy-aware mobile map design. The study contributes empirical evidence to mobile cartography research and connects interface design decisions to sustainability considerations.