Visibility of color symbology in head-up and head-mounted displays in daylight environments

Color-coded symbology has the potential to enhance the performance of people using head-up and head-mounted displays (HUDs and HMDs). The distinguishing feature of these displays is the optical combiner that presents symbology combined with the forward real-world scene. The presence of high-ambient daylight can desaturate the symbol colors, making them difficult to recognize. We defined a set of colors for testing based on color-coding conventions, color symbology research, and results from our previous testing. We then conducted a series of experiments to test the visibility and naming of color symbols and the legibility of color text mixed with daylight. Results were statistically analyzed and also modeled using color-difference formulae. Specific attention was given the symbol color blue, and an alternative blue color was proposed that had much higher visibility.