COLREGs
Navigation Lights for Boats — The Complete COLREGs Guide
Published · Last checked October 2026
Under the COLREGs a vessel underway shows a red sidelight to port, a green sidelight to starboard and a white sternlight, each over a set arc. A power-driven vessel adds a white masthead light (two if 50 m or longer). Extra all-round lights in vertical lines show what a vessel is doing: red over white is fishing, white over red a pilot, red over red not under command, and red-white-red restricted in ability to manoeuvre.
The basic lights and their arcs (Rule 21)
| Light | Colour | Arc |
|---|---|---|
| Masthead | White | 225°: right ahead to 22.5° abaft the beam each side |
| Sidelights | Green (starboard), red (port) | 112.5° each: right ahead to 22.5° abaft the beam |
| Sternlight | White | 135° centred right astern |
| Towing light | Yellow | 135° astern, above the sternlight |
| All-round | Any | 360° |
Minimum ranges (Rule 22)
| Vessel length | Masthead | Sidelights | Stern / all-round |
|---|---|---|---|
| 50 m or more | 6 | 3 | 3 |
| 20 m to 50 m | 5 | 2 | 2 |
| 12 m to 20 m | 3 | 2 | 2 |
| Under 12 m | 2 | 1 | 2 |
Sailing vessels (Rule 25)
- Under sail: sidelights and sternlight. No masthead light.
- Under 20 m: may combine them in a tricolour at the masthead, which is more visible offshore. Never use the tricolour with the engine running.
- Optional: all-round red over green at the masthead, but not with a tricolour.
- Motor-sailing: you are a power-driven vessel, so show a masthead light, sidelights and sternlight, and a cone point down by day.
Vessels you must recognise
| Vessel | Lights |
|---|---|
| Trawling | Green over white |
| Fishing (not trawling) | Red over white |
| Not under command | Red over red |
| Restricted in ability to manoeuvre | Red, white, red |
| Constrained by draught | Three reds, plus normal power-driven lights |
| Pilot on duty | White over red |
| At anchor (under 50 m) | One all-round white forward |
| Aground | Anchor light(s) plus red over red |
| Towing (tow under 200 m) | Two masthead lights in a vertical line, plus a yellow towing light above the sternlight |
See every one at night from any angle in the COLREGs lights trainer and print the navigation lights cheat sheet.
The lights rules in full
- Rule 20: Application of Part C
- Rule 21: Definitions of lights
- Rule 22: Visibility of lights
- Rule 23: Power-driven vessels underway
- Rule 24: Towing and pushing
- Rule 25: Sailing vessels underway and vessels under oars
- Rule 26: Fishing vessels
- Rule 27: Vessels not under command or restricted in their ability to manoeuvre
- Rule 28: Vessels constrained by their draught
- Rule 29: Pilot vessels
- Rule 30: Anchored vessels and vessels aground
Related guides
Frequently asked questions
Do sailing boats need a masthead light?
Not under sail. A sailing vessel shows sidelights and a sternlight (or a tricolour if under 20 m). With the engine on she is a power-driven vessel and must show a steaming (masthead) light.
When should navigation lights be on?
From sunset to sunrise and in restricted visibility, under Rule 20.
Can I use a tricolour and deck-level lights at the same time?
No. Show one or the other, never both.