39 Spring 2025 Proceedings with highly salient properties are also likely to capture attention, reducing search efficiency through momen- tary distraction.24 For example, searching for a person in the debris field of a capsized boat where a bright red crab pot buoy may stand out. Top-down attentional, or goal-directed, guidance is internal to the observer’s search intentions.25 This guid- ance originates from the observer’s knowledge or beliefs about a given task that guides their search and influ- ences what is selected in their visual field. In contrast to stimulus-driven attentional capture, top-down guid- ance may depend on the attentional set of the searcher, or information provided to the searcher that influences what is selected for attention.26 Physical salience alone will not involuntarily capture attention, unless it is con- gruent with the attentional set. A real-world example is if SAR responders are told that crewmembers from a ship in distress have abandoned ship and are now on a green life raft. The SAR responders can establish their attentional set to guide their search for green as opposed to other colors in the environment. Multiple-color visual search studies suggest that sin- gle-color guidance is more efficient than multiple-color guidance.27 For example, a SAR responder’s search can be guided by the color orange, but not simultaneously by both orange and green. Holding a color in working memory while searching for a second color increased error rates among observers, and is theorized to have placed a load on working memory that interfered with prespecified search guidance.28 A recent study provided evidence that two attentional templates—two colors— can be active simultaneously, though search perfor- mance decreases were unclear.29 A similar study found that two colors could be attended to and improved per- formance in comparison to no color guidance, but single- color guidance performed best.30 Interestingly, two search targets that are close in color, like orange and red, had faster response times than two distinctly different-colored targets, like orange and green.31 Thus, while multiple-color attentional guidance is possible, it appears to come at a performance cost com- pared to single-color or similar color attentional guidance. Previous Color Studies The original 1955 Navy study found high color satu- ration and/or high brightness colors performed best among nonfluorescent colors, with the exception of hues of yellow and white which were often misidentified at a distance, or not detected at all.32 Since SAR operations often occur in rough seas with abundant white caps, yel- lows and whites were excluded as acceptable lifesaving equipment colors. Hues of orange and red, while not the most detectable colors in all environmental conditions, performed best on average across the broadest range of conditions.33 Due to concerns in the mid-1950s with the color per- manence of fluorescent dyes and paints, fluorescent colors were not considered for lifesaving equipment. However, the 1955 Navy report concluded the detectability of flu- orescent yellow-orange and fluorescent red-orange far exceeded all nonfluorescent colors.34 Fluorescent colors have been shown to involuntarily attract the attention of observers, both in direct and peripheral vision.35 They are more conspicuous during daylight hours, including the low-light times of dusk and dawn, than standard colors.36 Considerable improvements have been made to fluorescent color permanence in the past 70 years, par- ticularly in terms of ultraviolet light degradation. Color permanence concerns continue to appear in literature, and the degree of color permanence appears to vary greatly among fabrics, dye processes, coatings, and base materials.37 Color patterns are another means of increasing con- spicuity by drawing the attention of observers. Multiple patterns are currently used in highway safety and emer- gency response. While there has been work on identi- fying a single most effective pattern, an overarching theme is placing highly contrasting colors in a pattern not occurring in nature. The colors used in these pat- terns tend to be high chromaticity colors adjacent to high luminance colors, such as the red and yellow chevron recommended for fire apparatus.38 Importantly, visual search in a maritime domain can be over several nauti- cal miles and the patterns may lose visual effectiveness, or conspicuity. The Way Forward The RDC published a comprehensive lifesaving equipment colors literature review in 2023. Four col- ors—gleaned from the literature review, CG-ENG-4, and maritime industry input—were identified for RDC field experiments conducted in Long Island Sound on August 21, 2024, demonstrate how the physical salience of a target varies with environmental conditions including sun angle, which affects the apparent color of water. Coast Guard photo by Joshua Pennington
