[nathanww]

A thing to keep in mind is that this person is sitting behind a plexiglass shield, at an unpredictable angle relative to the robot, possibly with obstructions(other robots) in the line of sight. This means that recognition based on a shape or pattern like a barcode probably won't work, which leaves you with just using color as a beacon. Even with just a bright orange hat or something, the robot has to be able to pick up that signal and distinguish it from the background, which can be tricky in and of itself.