Red and green buoys mark the two edges of a channel — but which colour belongs on which side depends on where you're sailing. Every lateral buoy's meaning is read against the direction of buoyage, generally the direction of a boat returning from open sea; where that direction isn't obvious, the chart prints an arrow showing it. From there, the world splits into two systems. In IALA Region A (Europe, Africa, most of Asia and Oceania), returning from sea you keep red marks to port and green to starboard. In IALA Region B (the Americas, Japan, Korea, the Philippines), it's reversed: green to port, red to starboard. Shape backs up colour either way — a flat-topped can always marks one side, a pointed cone or "nun" the other, in both regions.
A stop sign is red in Bangkok and in Boston. A buoy isn't. Sail from a marina in England to one in Florida and the colours on either side of the same kind of channel entrance swap, while the shapes stay exactly where you'd expect them. That isn't a design flaw — it's two different, internally consistent regional systems, and knowing which one you're looking at is the whole trick. This article walks through the reference every lateral buoy's colour depends on, compares the two world regions side by side, and explains why the classic "red right returning" trick only works in one of them, plus how shape, light, and a plain unlit post carry the same message when colour alone won't do.
Direction of Buoyage: The Reference Every Colour Depends On
A lateral mark's colour means nothing on its own — it only makes sense read against a reference called the direction of buoyage. Generally, that's the direction a boat takes returning from open sea, or heading upstream into a river or estuary.
Where the geography doesn't make that direction obvious, the chart itself settles it: a dedicated arrow symbol is printed on the chart, the same sheet you'd already be reading for its title block and symbol legend. The same buoy, on the same channel, means the opposite side depending on which way you're travelling through it. That's true everywhere, before any regional colour system even enters the picture.
IALA Region A vs IALA Region B: Colours Swap, Shapes Don't
The world's lateral buoyage is split into two regions, and every mark you see belongs to one of them.
In IALA Region A — Europe, Africa, and most of Asia and Oceania — returning from sea, you keep red marks to port and green marks to starboard. In IALA Region B — the Americas, Japan, Korea, and the Philippines — it's reversed: green marks to port, red marks to starboard.
Shape doesn't flip with colour. A can (cylindrical, flat-topped) always marks the port-hand side; a cone or "nun" (pointed) always marks the starboard-hand side. So Region A's port mark is a red can, and Region B's port mark is a green can — same shape, opposite colour. Neither region is the default; a sailor needs to know which one they're in.
"Red Right Returning" Only Works in Region B
"Red right returning" — keep red to starboard, your right hand, when returning — is a real, accurate, widely taught mnemonic. It's also a Region B rule, not a universal law of the sea.
A sailor who has that phrase memorized and then charters a boat in Region A waters would confidently, calmly pass a buoy on the wrong side, because in Region A red belongs to port, not starboard. Region A has its own regional teaching phrases pointing the opposite way, for the same reason: every short mnemonic like this is built for one region and breaks in the other.
It's also worth remembering that "returning" itself depends on knowing the direction of buoyage — the same reference from the first section. Get that wrong and even a mnemonic for the right region won't save you.
Shape, Topmark, and Light Carry the Same Message
Colour is only one channel of information, and it's the one that fails first in glare, dusk, or fog. Shape backs it up without needing colour at all: a can's flat top marks one side, a cone or nun's pointed top marks the other, in either region.
A topmark — a small shape, often a sphere, fixed above a mark — reinforces identity further, which matters most on a beacon, a fixed post with no colour advantage in poor light either. A lit mark's light is the same colour as its side, and its flash rhythm is printed on the chart beside the mark's symbol, so it can be told apart after dark. A daybeacon is simply the unlit version: a shape fixed to a post rather than a floating, lit buoy, carrying exactly the same lateral meaning as its coloured, lit cousin.
Where a Channel Splits: Preferred-Channel Marks
At a fork in a channel, a single buoy or beacon carries bands of both colours instead of just one.
One colour dominates the mark's body, with a single broad band of the other crossing it, and that dominant colour keeps its ordinary lateral meaning — shape included. A mostly-red can, banded with green, is still a can: read it and keep it exactly like any other red can. A mostly-green cone, banded with red, is still a cone: read it like any other green cone. Nothing new to learn here, just the same colour-and-shape habit from earlier in this article, applied to a mark that also happens to flag a fork. If lit, these marks flash in a distinctive rhythm reserved for exactly this kind of mark, in the dominant colour.
None of this needs memorizing perfectly on the first pass. What helps is one standing habit: read the chart in front of you — its direction-of-buoyage arrow, its symbol legend, and the mark's own colour and shape — rather than lean on a rule half-remembered from somewhere else. A mnemonic is a good shortcut once you know which region it belongs to, and a bad one the moment you cross into the other. Buoyage details are also corrected and occasionally revised, so it's worth a quick check of current local charts or notices before you sail somewhere new to you. SailStarter's short lessons work through exactly this kind of reading, buoy by buoy, until picking the right side stops being a guess.