More from the article ...

... The National Highway Traffic Safety Administration released proposed changes to Federal Motor Vehicle Safety Standard (FMVSS) No. 108, specifically rewriting the rules to fit autonomous vehicles. It's a mix of cutting red tape for human-free designs and standardizing how robotaxis communicate with the world around them -- starting with a distinctive blue-green light.

NHTSA is proposing cyan-colored marker lamps "to clearly and consistently signal to law enforcement and other road users when an automated driving system is operating the vehicle."

Why cyan? The auto industry already uses red, amber, white, and flashing blue/red lights for such things as brakes, turn signals, headlights, and emergency vehicles. Cyan could theoretically fill the visual gap without confusing road users.

And there's some precedent, too. Mercedes-Benz got state-level approval for turquoise lights on its Level 3 Drive Pilot cars -- even though the automaker has since scrapped the idea in favor of a Level 2++ system. Nevertheless, NHTSA wants to set a national standard that robotaxi operators like Waymo, Nuro, and Zoox, as well as automakers like GM and Mercedes, can adopt uniformly.

Under the proposed rule, cyan marker lights would be optional for manufacturers. However, by creating official federal standards for their color, brightness, and location, NHTSA wants to make sure that any automaker who chooses to add them uses a consistent, legal setup instead of a confusing mix of different colors and signals.

NHTSA is also proposing to get rid of some lighting requirements that wouldn't make sense for a vehicle without a human driver. ...