Why do ships and aircraft use red and green lights for port and starboard? Were these colors an arbitrary choice?

  Why are ships red below the waterline?

Published By Thinking Boxx June 16 2021 | 18:45 PM IST |

Actually there was/is no real reason as far as I know - ships below the waterline are painted with antifouling paint and I think in the past this had a high lead and copper (oxide) content and this made the paint red. These days you will find all sorts of colours below the waterline - but for commercial ships I would guess red is still the most common colour. The color thing was kicked off by the British Admiralty in 1847 by standardizing that Green be Right and Red be Left. I don’t think there was a reason for the left/right decision. There had been lights on vessels before that but some were red/green while others were green/red (confusing)! Within a dozen years or so the British standard was adopted by nearly all seafaring nations of the world.

The terms Port and Starboard go way back. Since the majority of folks are right handed, the steering oar on OLD vessels (Vikings, etc.) was on the right side before somebody came up with the “technology” to put it in the middle. Hence, “starboard/steerboard” and the steering board was always placed on the outside with the ship secured to a dock to protect against damage. So now you have the steerboard side of a vessel and the other side (against the dock) became the “port” side”. Kind of cool when ya think about it.

When aircraft became a known commodity it was initially seen as a ship (vessel) that flew. The “leader of the pack” was still called Captain and the second pilot was still the “First Officer”. When transoceanic flying game to be (1930s) aircraft normally carried two crews . The Captain made the takeoff and as soon as he was satisfied, he turned it over to the First Officer (and crew) for the first watch (4 hours - just like aboard ship). After 4 hours, the first crew came back on. When it was time to arrive the Captain was back in the seat for the landing.

So now I’m wondering why Starkey chose to put a Blue dot on the left hearing aid and a Red dot on the right. Red on the right does sound reasonable but after 170 years, the world has pretty much standardized. Go figure!

there is a reason and it’s not arbitrary at all. What’s important to know is that the green light is on the starboard side and the red light is on the port side.

As a result when two ships or aircraft are converging, the one on the right will see a green light and the one on the left a red.

In other words, the vehicle with the right of way sees green, as in go, and the vehicle on the left, which should give way, sees a red, as in stop.

The additional bit of information is that the combination of lights seen tells you the orientation of the other vehicle so you can assess whether you are closing or separating and what to do to avoid a collision.

And this is what happens quite quickly if you don’t paint antifouling paint on the bottom of your vessel!! A lot of them aren’t anymore. Used to be, the paint used to protect them from corrosion in salt water had a lot of copper oxide and it had a red hue, so they just made it red. But modern paints have been developed that work as well without the copper oxide in it. If you look at modern ships, many are painted black below the waterline now. I know that at some point the USS Saratoga had a red bottom, but then later it was black. And this video of the Carl Vinson entering dry dock shows that it had a gray bottom.

Carrier USS Carl Vinson Enters Drydock for Maintenance After Busy Deployment Cycle - USNI News

USS Carl Vinson (CVN-70) entered a drydock at the Puget Sound Naval Shipyard in Washington for a docking planned incremental availability. Red is a commonly used color for underwater coatings. But anti-fouling paint chemistry has evolved considerably in recent decades, where just about any color is possible. Red is still popular traditionally, but many colors can be seen out there, including green, black, blue, and others. See the guided-missile cruiser

And this photo of the USS Seattle undergoing maintenance. All black on the bottom.

Tim Malcolm Hughes.

And both red and black don’t look the worse for wear with the start of bottom growth. While the toxic compounds used in the past had a role in the pigmentation of bottom coatings, that has changed. The emphasis today is more on coatings that are environmentally friendly and less toxic to marine life. Good luck

Picture Source Wikipedia

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