Harlequin bug, Murgantia histrionica (Hahn), is an important pest of Brassica crops in the southern United States. Regional populations are highly variable and unpredictable from farm-to-farm, and therefore accurate monitoring of activity would greatly improve IPM decision-making and the timing of control tactics. To our knowledge, there is no monitoring device or proven trapping system for this pest. We contribute new knowledge of harlequin bug visual ecology, which will aid in the development of an effective trap. In both lab and field color choice experiments, harlequin bug adults and large nymphs responded positively to green and black colors, and statistically less frequently to yellow, white, purple, or red with the exception of adult females, which were most attracted to red and green in the lab, but green and black in the field. We conclude that future trapping devices for harlequin bug should be green or black in color.