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The Colour and Shape of Navigation Marks

Most navigators, even inexperienced ones, learn that colours are important when trying to identify navigation marks at sea. And most people also know that there are red and green ones.

It is equally true that many find it confusing trying to remember which side of the channel we should expect to find them. Ie. What are they indicating?

Part of the confusion stems from the fact that there are two common (and unfortunately opposite) international (IALA) systems:

System A) used in Europe, Africa, Australasia and parts of Asia and

System B) one used in the Americas and parts of East Asia, including Japan.

In system A the red marks indicate the left side of the channel, green equals right side of the channel when you are heading home, from sea towards land.

In system B, the opposite is true.

There are two good ways of remembering your system. The key is to pick your one and stick to it – and do your best to forget the other one.

System A

In System A: Red is on your left and green is on your right when you are returning home.

“Is there any port left?” Is one saying that is taught for this system, as if you are asking a dinner companion whether there is any fortified wine left in the decanter. I’m guessing it’s an old Royal Navy saying.

I was taught that the system is logical because you need clarity when you are tired and coming home to port, not when you are fresh and heading out to sea. And most people in system A countries find this way round – port marks on the left, starboard on the right – more intuitive and logical.

System B

In System B: sailors are taught ‘Red Right Returning‘.

Red marks are on your right as you head home. This is such a powerful alliterative saying that if you don’t sail in the Americas or another System B area, you’re advised to forget it as soon as possible!


Even those who are comfortable with the colour system are often unaware that there is a shape system for these lateral marks at work at the same time. But why?

We are always at the mercy of the elements at sea and there are so many times when low light or a low sun or poor visibility makes it hard to pick out colour. The atmosphere has a habit of stealing colour from objects as light is scattered by moisture and particles in the air near the sea. The effect leaves us feeling colour blind.

But even when the colour has disappeared from a buoy or mark, the shape is still often easy to make out, as a silhouette effect.

See for Yourself

Have a look at the two navigation marks below and you’ll notice that close up the colour is fairly easy to work out, but from a distance it grows much harder. But even at a distance we can see that the red mark is shaped like an upside down bucket and the green mark is cone-shaped.

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