Light and dark are used pervasively to represent positive and negative concepts. Recent studies suggest that black and white stimuli are automatically associated with negativity and positivity. However, structural factors in experimental designs, such as the shared opposition in the valence (good vs. bad) and brightness (light vs. dark) dimensions might play an important role in the valence–brightness association. In 6 experiments, we show that while black ideographs are consistently judged to represent negative words, white ideographs represent positivity only when the negativity of black is coactivated. The positivity of white emerged only when brightness and valence were manipulated within participants (but not between participants) or when the negativity of black was perceptually activated by presenting positive and white stimuli against a black (vs. gray) background. These findings add to an emerging literature on how structural overlap between dimensions creates associations and highlight the inherently contextualized construction of meaning structures.