External Human-Machine Interfaces: Which of 729 Colors Is Best for Signaling 'Please (Do not) Cross'?

Future automated vehicles may be equipped with external human-machine interfaces (eHMIs) capable of signaling to pedestrians whether or not they can cross the road. There is currently no consensus on the correct colors for eHMIs. Industry and academia have already proposed a variety of eHMI colors, including red and green, as well as colors...