MASTER COLOUR CHART
Learn the function, not just the fixture name. This chart follows FAA airport-lighting guidance.
| AGL light | Colour | Main function |
|---|---|---|
| Runway edge | White | Defines runway edges |
| Runway edge, caution zone | Yellow / amber | Caution zone: limited runway remaining (instrument runways) |
| Runway threshold | Green | Identifies landing threshold (seen by the approaching aircraft) |
| Runway end | Red | Identifies runway end (seen from the runway, looking toward the end) |
| Runway centreline | White | Runway guidance |
| RCL near runway end | White / red alternating | Caution: last 3,000 to 1,000 ft remaining |
| RCL final section | Red | Danger: last 1,000 ft remaining |
| Touchdown zone | White | Touchdown guidance (threshold to 3,000 ft or runway midpoint) |
| Taxiway edge | Blue | Defines taxiway edges |
| Taxiway centreline | Green | Taxi guidance |
| Taxiway lead-on / lead-off | Green / yellow | Alternating green / yellow: within the runway environment or ILS critical area |
| Clearance bar | Yellow | Holding-position conspicuity |
| Runway guard light | Flashing yellow | Runway-intersection warning |
| Stop bar | Red | STOP |
| Runway entrance lights (REL, FAA RWSL) | Red | Unsafe to enter or cross the runway (automatic, surveillance-driven) |
| Take-off hold lights (THL, FAA RWSL) | Red | Unsafe to take off (at the runway departure position) |
| REIL | White | Runway-end identification (flashing, facing the approach) |
| PAPI | White / red | Vertical approach guidance |
| Approach lighting | White (generally) | Approach alignment / guidance |
| CAT II/III approach side-row elements | Red (applicable configurations) | Enhanced approach guidance |
One-minute memory
- WHITE = runway / approach / TDZ
- GREEN = threshold / taxiway centreline
- BLUE = taxiway edge
- YELLOW = warning / holding / guard
- RED = stop / runway end
RUNWAY LIGHTING COLOURS
Runway edge
Normally white. On instrument runways, FAA guidance uses yellow / amber in the caution zone at the far end, replacing white for the last 2,000 ft or half the runway length, whichever is less.
Threshold and end
The lights at the runway end are two-colour. They emit green outward from the runway end, marking the threshold for landing aircraft, and red toward the runway, marking the end of the runway for a departing aircraft.
Runway centreline lights (FAA sequence)
One of the most common exam questions. FAA AIM describes it as seen from the landing threshold: white, then alternating white / red, then red. The distances below are runway remaining.
| Position | Colour |
|---|---|
| More than 3,000 ft remaining | White |
| 3,000 ft to 1,000 ft remaining (a 2,000 ft zone) | Alternating white / red |
| Last 1,000 ft | Red |
Touchdown zone lights are steady-burning white, in two rows of transverse light bars either side of the centreline. They start 100 ft beyond the landing threshold and extend to 3,000 ft beyond it, or to the runway midpoint, whichever is less.
FAA vs ICAO caution zones (Annex 14)
| Item | FAA (AIM) | ICAO (Annex 14) |
|---|---|---|
| Runway edge, yellow caution zone | Last 2,000 ft or half the runway, whichever is less | Last 600 m or one-third of the runway, whichever is less |
| Centreline, alternating red / white | 3,000 ft to 1,000 ft from the end | 900 m to 300 m from the end |
| Centreline, all red | Last 1,000 ft | Last 300 m |
ICAO values are quoted from Annex 14 Volume I, Chapter 5. Confirm against the edition applicable to your project.
TAXIWAY LIGHTING COLOURS
Edge = Blue
Defines the lateral edge of the taxiway.
Centreline = Green
Steady-burning green giving taxi guidance, particularly in low visibility.
Lead-on / lead-off lights
Lead-off lights guide aircraft exiting the runway and lead-on lights guide aircraft entering it. Both alternate green and yellow, starting with green at the runway centreline, to warn that the aircraft is within the runway environment or ILS critical area. The pattern ends one light position beyond the holding position.
This is FAA usage. In ICAO and UK usage, “lead-on lights” usually means the steady green centreline lights that lead an aircraft from a stop bar onto the runway, so confirm which standard a question uses (see Note 03).
BLUE BLUE
● ●
│ GREEN │
│ ● │
│ ● │
BLUE BLUE
EDGE = BLUE CENTRE = GREEN
HOLDING POSITION LIGHTS
Clearance bar
Three steady-burning in-pavement yellow lights that increase conspicuity of a holding position or mark a taxiway intersection in applicable locations.
Runway guard lights (RGL)
Enhance the conspicuity of a runway/taxiway intersection, especially in low visibility. The FAA describes elevated (a pair of flashing yellow lights) and in-pavement (alternately flashing yellow) configurations.
Stop bar
Red, steady-burning, unidirectional in-pavement lights across the taxiway at the runway holding position, with elevated red lights on each side where provided. Controlled stop bars are coordinated with taxiway centreline lead-on lights.
Stop bar vs runway guard light
| System | Colour | Message |
|---|---|---|
| Stop bar | Red | STOP |
| Runway guard light | Flashing yellow | Runway-intersection warning / conspicuity |
RUNWAY
════════════════════════
● ● ● ● ● ● ● STOP BAR (red lights, in pavement)
─────────────────────── HOLDING-POSITION MARKING (yellow)
TAXIWAY
LIGHT = red stop bar
MARKING = yellowMemory
- STOP = RED
- WARNING = YELLOW
PAPI COLOURS
PAPI uses white and red to show whether the aircraft is above, on or below the intended approach path. The pilot sees the visual output, not the internal lamp or filter technology.
| Display | Meaning |
|---|---|
| 4 white | Too high |
| 3 white + 1 red | Slightly high |
| 2 white + 2 red | On path |
| 1 white + 3 red | Slightly low |
| 4 red | Too low |
Memory
- More white = high
- 2W + 2R = on slope
- More red = low
APAPI (two units) uses the same colours: 2 white = high, 1 white + 1 red = on path, 2 red = low.
See PAPI & APAPI for aiming and installation.
APPROACH LIGHTING AND REIL
Approach lighting
The general FAA approach-lighting system uses white for primary guidance. Certain CAT II/III configurations include red side-row elements, providing runway alignment, height perception, roll guidance and horizontal reference. The approach ends at the green threshold lights. ICAO CAT II/III systems also use red side-row barrettes in the inner section; check Annex 14 for the exact extent.
REIL
Runway End Identifier Lights are white flashing lights used to identify a runway end or threshold. They may be unidirectional (facing the approach) or omnidirectional.
LIGHTS VS MARKINGS VS SIGNS
Do not apply the light-colour chart to markings or signs.
| Item | Typical FAA colour |
|---|---|
| Runway markings | White |
| Taxiway and holding-position markings | Yellow |
| Mandatory sign | White inscription on red background |
| Location sign | Yellow inscription on black background |
| Direction / destination sign | Black inscription on yellow background |
| Runway distance remaining sign | White numeral on black background |
Sign colours are written as inscription on background, per FAA AC 150/5340-18H (issued September 2024). Always read the background colour first: red = mandatory, black = location, yellow = direction, destination and information.
More detail: Runway Markings vs Lighting and Taxiway Signs & Markings.
EXAM TRAPS
Colour alone is never enough. Always ask: what colour, where is it, and what is its function?
Red is not always "stop"
Red can mean runway end, stop bar, FAA runway entrance lights, a PAPI low indication or CAT II/III approach elements. Location and function decide.
Yellow is not automatically taxiway edge
Yellow can be runway caution-zone edge lights, clearance bars, runway guard lights or lead-on/lead-off elements. Taxiway edge is blue.
Blue vs green
Blue = taxiway edge. Green = taxiway centreline. The most important colour pair.
Green is not just "taxiway"
Green is both the runway threshold (from the approach) and the taxiway centreline. It is not the runway centreline.
Threshold vs centreline
A green threshold does not mean a green runway centreline. Runway centreline is white, with the specified colour transition toward the end.
Stop bar vs RGL
Stop bar red = STOP. Runway guard light yellow = warning.
SCENARIOS
| You see | Answer |
|---|---|
| BLUE along both sides of a taxiway | Taxiway edge lights |
| GREEN in the centre of a taxiway | Taxiway centreline lights |
| RED across a taxiway at the runway holding position | Stop bar |
| YELLOW at a runway/taxiway intersection | Likely runway guard lights, subject to the exact configuration |
| GREEN at the runway threshold from the approach side | Threshold lights |
| PAPI shows 2 white + 2 red | On the nominal visual approach path |
10 MUST-KNOW COLOURS
| # | Light | Colour | # | Light | Colour |
|---|---|---|---|---|---|
| 1 | Runway edge | White | 6 | Taxiway edge | Blue |
| 2 | Runway threshold | Green | 7 | Taxiway centreline | Green |
| 3 | Runway end | Red | 8 | Stop bar | Red |
| 4 | Runway centreline | White (then white/red, red) | 9 | Runway guard light | Flashing yellow |
| 5 | TDZ | White | 10 | Clearance bar | Yellow |
RAPID-FIRE QUESTIONS
What colour are runway edge lights?
White, with the specified yellow/amber caution-zone section on applicable instrument runways.
What colour identifies a runway threshold?
Green.
What colour identifies a runway end?
Red.
What colour are runway centreline lights?
Primarily white, then alternating white/red and then red toward the runway end under the FAA sequence.
What colour are touchdown-zone lights?
White.
What colour are taxiway edge lights?
Blue.
What colour are taxiway centreline lights?
Green.
What colour is a stop bar?
Red.
What colour are runway guard lights?
Flashing yellow.
What colour are clearance-bar lights?
Yellow.
What colours does PAPI use?
White and red.
What colour are runway markings?
White.
What colour are taxiway markings?
Yellow.
What does a red stop bar mean?
Stop.
What does blue taxiway edge mean?
Taxiway lateral boundary.
What colours do FAA lead-on / lead-off lights use?
Alternating green and yellow, starting with green at the runway centreline.
What colour are runway entrance lights in the FAA RWSL system?
Red: it is unsafe to enter or cross the runway.
FINAL EXAM MEMORY
Runway is white, threshold is green, runway end is red. Taxiway edge is blue, taxiway centreline is green. Stop bar is red; runway guard and clearance bar are yellow. PAPI is white + red. The runway centreline goes white → white/red → red. Always confirm the exact application, directionality and colour transitions against the applicable fixture, system and current standard.
ENGINEERING & EXPERT NOTES
Colour Meaning Depends on Position and Pattern
PrincipleLearn the colour together with where it appears and what it marks. The same colour can mean different things in different places.
Check Colour From the Pilot's Viewing Direction
InspectionA light can show a different colour or none from the opposite direction. Verify from the intended view.
Measure Chromaticity, Don't Trust the Eye
VerificationLED colour can drift. Use an instrument for acceptance and periodic checks.
Use Approved Filters and Lenses Only
SparesA generic coloured part can change both colour and intensity. Replace with the approved part for that fixture.
REFERENCES & FURTHER READING
| # | Source | Use it for |
|---|---|---|
| 1 | FAA AIM, Chapter 2 Section 3: Airport Marking Aids and Signs | Runway, taxiway and holding-position marking colours. |
| 2 | FAA AC 150/5340-18H – Standards for Airport Sign Systems | Sign colours and layout. |
| 3 | FAA AIM, Chapter 2 Section 1: Airport Lighting Aids | Runway centreline sequence, TDZ, lead-on/lead-off, clearance bars, RGL, stop bars. Verify the current text. |
| 4 | ICAO Annex 14 Volume I, Chapter 5 – Visual Aids for Navigation | ICAO caution-zone and centreline sequences for ICAO projects. |
| 5 | FAA AC 150/5340-30J – Design and Installation Details for Airport Visual Aids | Installation details for taxiway, stop bar, guard light and clearance bar colour layouts. |
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