What do the coloured lights on aircraft and at airports mean?

At a glance

Aerodrome lighting

ICAO Annex 14 Vol. I, 9th Edition (July 2022)

Aircraft position lights

Red left · green right · white rear

Runways and taxiways

Runway edge white · threshold green · runway end red · taxiway edge blue · taxiway centreline green

US colour limits

14 CFR 25.1397 (CIE chromaticity)

Position lights borrowed from the sea

Aircraft navigation lights copy the maritime convention: red on the left (port) side, green on the right (starboard) side, and white at the rear. US certification rules for transport aeroplanes place the red and green forward lights as far apart as practicable, with red on the left and green on the right in normal flight, and a white rear light as far aft as possible. The logic is geometric. If you see red on the left and green on the right, the aircraft is coming towards you; red alone means it is crossing from your right to left; white alone means you are behind it. Anti-collision beacons and strobes, in red or white, flash separately to draw attention.

A colour map painted in light

At night an aerodrome is a pattern of coloured lines. Runway edge lights are white, but on instrument runways the last part turns yellow to form a caution zone. Centreline lights on precision runways are white until near the end, then alternate red and white, then turn fully red for the final stretch, so a pilot rolling out can judge how much runway is left. The runway end shows red towards the runway and green outwards towards arriving aircraft, marking the threshold. Taxiway edges are blue and taxiway centrelines green. The colour tells the pilot what kind of surface they are on and which way is safe, often in visibility where markings on the ground cannot be seen.

Blue appears only on taxiway edges, so a pilot who sees blue knows they are not on a runway — a whole category of surface identified by one hue.

Glide-slope lights: red means low

Visual approach-slope systems use colour to show the aircraft's angle. A precision approach path indicator is a row of light units that each show white above a certain angle and red below it, so a pilot on the correct slope sees an even mix; all red means dangerously low, all white means high. Older visual approach slope indicators work the same way with two or three bars. Some smaller fields use a single tri-colour unit where amber means high, green on slope and red low. The principle is the same across all of them: red is reserved for the direction that ends with the ground.

Specifying the colours

Aviation lights are defined as regions of the CIE chromaticity diagram rather than by name. The US rule for aircraft position lights sets limits for aviation red, green and white in chromaticity coordinates; ICAO Annex 14 does the same for aeronautical ground lights and for markings and signs. Because pilots may have to identify a single light at night with nothing to compare it against, the regions are drawn to keep red, green, yellow, blue and white well apart. Pilots are also screened for colour vision, and the tests used are tied to the practical task of identifying these signal colours.

The data

How to check it yourself

1. At night, look at an aircraft's wingtips: red on the left and green on the right means it is heading towards you.
2. For aerodrome lighting details, the FAA's Aeronautical Information Manual is free; ICAO Annex 14 is the international source.
3. For certification colour limits, read the chromaticity definitions in the applicable regulation, not a colour name.

What the evidence says

Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.

• FactStrong evidence

  ICAO Annex 14 Volume I, Aerodrome Design and Operations, is in its 9th Edition dated July 2022, incorporating Amendment 18.

  Source: ICAO Annex 14 — Aerodromes, Volume I: Aerodrome Design and Operations

• StandardStrong evidence

  US rules for transport-category aeroplanes require a red forward position light on the left, a green one on the right and a white rear position light.

  Source: 14 CFR 25.1385 — Position light system installation

• FactStrong evidence

  According to the FAA, runway edge lights are white with yellow replacing white on the last portion of instrument runways, runway end lights show red towards the runway and green outwards, taxiway edge lights are blue and taxiway centreline lights are green.

  Source: Aeronautical Information Manual, Chapter 2 Section 1: Airport Lighting Aids

• StandardStrong evidence

  US regulations define aviation red, aviation green and aviation white by limits on their CIE chromaticity coordinates.

  Source: 14 CFR 25.1397 — Color specifications

Related questions

Why is the red light on an aircraft's left wing?

Aviation copied the maritime rule of red to port (left) and green to starboard (right), so the relative position of the two colours shows another aircraft's direction of travel.

Why are airport taxiway lights blue?

Blue marks taxiway edges so they cannot be mistaken for runway lights, which are white, red, green and yellow. Taxiway centrelines use green.

What does all red on a PAPI mean?

That the aircraft is well below the intended glide path. An even split of red and white means on slope; all white means too high.

Related topics

Go further

Sources

• ICAO Annex 14 — Aerodromes, Volume I: Aerodrome Design and Operations — International Civil Aviation Organization (Official standard or government)
• 14 CFR 25.1385 — Position light system installation — US Electronic Code of Federal Regulations (Official standard or government)
• Aeronautical Information Manual, Chapter 2 Section 1: Airport Lighting Aids — US Federal Aviation Administration (Official standard or government)
• 14 CFR 25.1397 — Color specifications — US Electronic Code of Federal Regulations (Official standard or government)

Reviewed 29 September 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.