Regions A and B
The system has two regions that differ only in the colour of the lateral marks. In Region A — Europe, Africa, most of Asia and Australasia — port-hand marks are red and starboard-hand marks are green. In Region B — the Americas, Japan, Korea and the Philippines — the colours are reversed, captured by the memory aid 'red right returning'. The direction of buoyage, which defines what counts as 'entering', is shown on the chart and generally runs clockwise around land masses and into harbours from seaward.
| Mark | Region A day | Meaning |
|---|---|---|
| Lateral — port | Red can, red light | Keep to port when entering |
| Lateral — starboard | Green cone, green light | Keep to starboard when entering |
| Cardinal | Black/yellow bands, double cones | Pass to the named (N/E/S/W) side of the danger |
| Isolated danger | Black with red band, two black spheres | Small danger with navigable water all round |
| Safe water | Red/white vertical stripes | Landfall or mid-channel; safe water all round |
| Special | Yellow, X topmark | A special area, not primarily navigational |
| IALA marks and their meaning (Region A colours). |
Cardinal marks and lights
Cardinal marks indicate the side on which it is safe to pass a danger, using black and yellow bands and paired cone topmarks that point the way to remember them: the north mark's cones both point up (black band on top), the south mark's both point down (black band at the bottom). At night their white lights use quick or very-quick flashing groups — continuous for north, three flashes for east, six plus a long flash for south, and nine for west — so a mark can be identified in the dark. Recognising light characteristics, colours and periods is exactly what the examiner tests.
TIP — Read the topmark first When you identify a cardinal mark, read the topmark cones: points-up is north, points-down is south, points-together is south's neighbour... learn the clock-face pattern once and the lights follow (3, 6+LFl, 9 o'clock).
WARNING — Confirm the region before you trust a colour Cross a boundary between IALA regions and the lateral colours swap. On any passage that changes region, note it on the plan so a red buoy is never read as the wrong side of the channel.