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Data and fibre colours.Pins, pairs, tubes and jackets.

The colour codes behind network, telephone and fibre cabling: T568A and T568B pinouts, crossovers and PoE, the 25-pair telephone code, UK BT socket colours and the TIA-598 fibre, jacket and connector colours. Every section lists its sources and how well they agree.

Twisted pair. T568A and T568B.

Both schemes use the same four colour pairs on the same RJ45 plug. The only difference is that the orange and green pairs swap places. Pick one scheme and use it at both ends of every link.

12345678
T568B, contacts facing you, clip away, pin 1 on the left.
Wiring scheme
Highlight the pins used by

All eight conductors are terminated on every outlet and patch lead, whatever speed the link runs at.

Pair 1
Blue, pins 4 and 5
Pair 2
Orange
Pair 3
Green
Pair 4
Brown, pins 7 and 8

Swipe the table sideways to see every column.

RJ45 pin colours for T568A and T568B with the signals carried on each pin
PinT568AT568B10/100Gigabit and fasterPoE
1White/greenPair 3White/orangePair 2Transmit +Data, both directionsAlt A (data pair)
2GreenPair 3OrangePair 2Transmit −Data, both directionsAlt A (data pair)
3White/orangePair 2White/greenPair 3Receive +Data, both directionsAlt A (data pair)
4BluePair 1BluePair 1Not usedData, both directionsAlt B (spare pair at 10/100)
5White/bluePair 1White/bluePair 1Not usedData, both directionsAlt B (spare pair at 10/100)
6OrangePair 2GreenPair 3Receive −Data, both directionsAlt A (data pair)
7White/brownPair 4White/brownPair 4Not usedData, both directionsAlt B (spare pair at 10/100)
8BrownPair 4BrownPair 4Not usedData, both directionsAlt B (spare pair at 10/100)

T568A and T568B pin colours

Verified

Pin colour assignments agree across a university IT standard page, a UK distributor and Intel.

  1. Nebraska Wesleyan University IT Support: Cabling Color Codes (opens in a new tab)T568A and T568B pin 1 to 8 colours; 25-pair major and minor colour sequence and tip/ring
  2. Rapid Electronics: Ethernet cable colour codes (opens in a new tab)T568A and T568B pin colours, pin 1 orientation, A-to-B crossover, T568B common in UK commercial work
  3. Intel Support: Ethernet cable pinouts (article 000007187) (opens in a new tab)10/100 uses pins 1, 2, 3 and 6; crossover 1-3 and 2-6; gigabit crossover adds 4-7 and 5-8
  4. Fluke Networks: Wire map testing, it is not all about colour (opens in a new tab)T568A puts orange on pins 3-6, T568B puts green there; mixing schemes causes crossed pairs
  5. Fiber Optic Association: Uncle Ted's guide to UTP termination (opens in a new tab)A and B differ only by swapping pairs 2 and 3; pair colours; crossovers not needed at 1G and above

Checked 9 Nov 2026

Pairs used by 10/100, gigabit and crossovers

Verified

Pin functions from Cisco and Intel documentation.

  1. Cisco: Ethernet 10BASE-T and 100BASE-TX pinouts (document 46792) (opens in a new tab)Transmit on pins 1 and 2, receive on 3 and 6; pins 4, 5, 7, 8 unused by 10BASE-T
  2. Intel Support: Ethernet cable pinouts (article 000007187) (opens in a new tab)10/100 uses pins 1, 2, 3 and 6; crossover 1-3 and 2-6; gigabit crossover adds 4-7 and 5-8
  3. Fiber Optic Association: Uncle Ted's guide to UTP termination (opens in a new tab)A and B differ only by swapping pairs 2 and 3; pair colours; crossovers not needed at 1G and above

Checked 9 Nov 2026

Which pairs carry what.

Older and slower links only use two pairs; gigabit and faster use all four in both directions. Power over Ethernet rides on top of the data.

10BASE-T and 100BASE-TX

Pins 1, 2, 3, 6

A device transmits on pins 1 and 2 and receives on pins 3 and 6. Pins 4, 5, 7 and 8 carry no data, but they should still be terminated so the cable works at higher speeds later.

Gigabit and faster

All 8 pins

1000BASE-T and the multi-gigabit and 10G versions send and receive on all four pairs at once. A single swapped, split or open conductor will drop a gigabit link back to 100 Mb/s or stop it working.

Power over Ethernet

Alt A or Alt B
  • Alternative A: power on the data pairs (pins 1, 2 and 3, 6)
  • Alternative B: power on pins 4, 5 and 7, 8
  • 802.3af (Type 1) up to 15.4 W and 802.3at (Type 2) up to 30 W use two pairs
  • 802.3bt Type 3 (60 W) and Type 4 (90 W) use all four pairs

Figures are the most the switch can supply. The device gets less once cable losses are taken off.

Power over Ethernet pairs and power

Corroborated

Power figures are the maximum at the switch (PSE); the device receives less after cable losses.

  1. Cisco: What is Power over Ethernet (PoE)? (opens in a new tab)802.3af/at/bt names and power levels; power on data pairs or spare pairs
  2. Microchip Developer Help: PoE terminology (opens in a new tab)PoE Types 1 to 4 (15.4, 30, 60, 90 W at the PSE), Alternative A and B pins, four-pair classes
  3. Linux kernel documentation: PSE power interface (opens in a new tab)Alternative A on pins 1, 2, 3, 6; Alternative B on 4, 5, 7, 8; spare pairs carry data at 1G and above
  4. Siemon: ANSI/TIA-568.2-E released (opens in a new tab)ANSI/TIA-568.2-E (2024) is the balanced twisted-pair standard; power delivery guidance added

Checked 9 Nov 2026

Crossover builder. See what each end does.

Choose how each end of a cable is terminated. The wire map shows where every conductor lands, just like a cable tester. Lines that change pin number are crossed.

End 1
End 2
Straight-through

Both ends use the same scheme, so every pin connects to the same pin at the far end. This is a normal patch lead or permanent link.

1→1, 2→2, 3→3, 4→4, 5→5, 6→6, 7→7, 8→8

End 1End 21122334455667788

Do you still need a crossover?

Almost never. Ports with auto MDI-X, which includes practically every gigabit port, sort out transmit and receive themselves. Use straight-through cables everywhere unless an old 10/100 device without auto MDI-X refuses to link.

A at one end, B at the other

This swaps the orange and green pairs: a 10/100 crossover. On a fixed link it is usually a mistake, made when two installers used different schemes. Testers report it as crossed pairs.

Full gigabit crossover

A true four-pair crossover also swaps blue with brown (pins 4 and 7, 5 and 8). It exists for old gigabit kit without auto MDI-X and is rarely made today.

The standards. Who says what.

Pin colours come from the North American TIA standard, but the same A and B layouts are used under the international and European cabling standards.

ANSI/TIA-568

The North American series that defines the T568A and T568B pin and pair assignments. The balanced twisted-pair part, ANSI/TIA-568.2, reached edition E in 2024 and now includes guidance on carrying power over data cabling.

ISO/IEC 11801

The international generic cabling standard for customer premises. Part 1 (2017) sets the common requirements for multi-vendor cabling that carries voice, data, video and power. It uses cabling classes rather than US category names.

EN 50173 and EN 50174

The European series, published in the UK as BS EN 50173. It covers generic balanced copper and optical fibre cabling for premises. Installation practice, including separation from power, sits in EN 50174-2.

IEC 60304

An older IEC standard that sets a palette of insulation colours for low-frequency telecoms cables and wires. It defines the colours themselves, not which conductor goes on which pin.

TIA-568, ISO/IEC 11801 and EN 50173

Verified

Standards summaries are taken from standards-body catalogue pages; the standards themselves are paid documents.

  1. Siemon: ANSI/TIA-568.2-E released (opens in a new tab)ANSI/TIA-568.2-E (2024) is the balanced twisted-pair standard; power delivery guidance added
  2. IEC Webstore: ISO/IEC 11801-1:2017 Generic cabling for customer premises (opens in a new tab)Title, edition and scope of ISO/IEC 11801-1
  3. iTeh Standards: EN 50173-1:2018 Generic cabling systems (opens in a new tab)EN 50173-1:2018 approved by CENELEC in 2018, replacing the 2011 edition
  4. BSI Knowledge: BS EN 50173-1 Generic cabling systems (opens in a new tab)EN 50173-1 covers balanced and optical fibre generic cabling for premises

Checked 9 Nov 2026

IEC 60304 standard insulation colours

Verified

IEC 60304 defines a palette of insulation colours for low-frequency cables; it does not set pinouts.

  1. IEC Webstore: IEC 60304:1982 Standard colours for insulation for low-frequency cables and wires (opens in a new tab)Title, edition 3.0 (1982) and scope of IEC 60304

Checked 9 Nov 2026

25-pair code. Five by five.

Multi-pair telephone cable uses five major colours and five minor colours. Each major colour runs through all five minors before the next major starts, giving 25 unique pairs. The tip wire is the major colour banded with the minor; the ring wire is the minor colour banded with the major.

  1. 1White/Blue
  2. 2White/Orange
  3. 3White/Green
  4. 4White/Brown
  5. 5White/Slate
  6. 6Red/Blue
  7. 7Red/Orange
  8. 8Red/Green
  9. 9Red/Brown
  10. 10Red/Slate
  11. 11Black/Blue
  12. 12Black/Orange
  13. 13Black/Green
  14. 14Black/Brown
  15. 15Black/Slate
  16. 16Yellow/Blue
  17. 17Yellow/Orange
  18. 18Yellow/Green
  19. 19Yellow/Brown
  20. 20Yellow/Slate
  21. 21Violet/Blue
  22. 22Violet/Orange
  23. 23Violet/Green
  24. 24Violet/Brown
  25. 25Violet/Slate

Top wire: tip (major colour, minor bands)Bottom wire: ring (minor colour, major bands)

Major (tip) colours

White, red, black, yellow, violet. Pairs 1–5 are white, 6–10 red, 11–15 black, 16–20 yellow and 21–25 violet.

Minor (ring) colours

Blue, orange, green, brown, slate, always in that order. The first four are the same pair colours used in Ethernet cable.

Binder groups

Bigger cables are built from 25-pair units, each wrapped in a binder ribbon or thread coloured in the same sequence: white/blue for pairs 1–25, white/orange for 26–50, and so on. Pair colours restart in every binder. 24 binders cover 600 pairs; larger cables add super-unit binders.

Binder group colours and the pairs they hold
GroupBinder colourPairs
1White/Blue1–25
2White/Orange26–50
3White/Green51–75
4White/Brown76–100
5White/Slate101–125
6Red/Blue126–150
7Red/Orange151–175
8Red/Green176–200
9Red/Brown201–225
10Red/Slate226–250
11Black/Blue251–275
12Black/Orange276–300
13Black/Green301–325
14Black/Brown326–350
15Black/Slate351–375
16Yellow/Blue376–400
17Yellow/Orange401–425
18Yellow/Green426–450
19Yellow/Brown451–475
20Yellow/Slate476–500
21Violet/Blue501–525
22Violet/Orange526–550
23Violet/Green551–575
24Violet/Brown576–600

25-pair colour code

Verified

The same five major and five minor colours are used by telephone cable makers worldwide.

  1. Nebraska Wesleyan University IT Support: Cabling Color Codes (opens in a new tab)T568A and T568B pin 1 to 8 colours; 25-pair major and minor colour sequence and tip/ring
  2. Access Communications: Multi-pair telephone cable colour code (opens in a new tab)25-pair major/minor colours, tip and ring, binder groups up to 600 pairs
  3. Caledonian Cables: Telephone cable colour codes and make-up (opens in a new tab)25-pair tip and ring colours, binder group sequence and super-unit binders

Checked 9 Nov 2026

Binder groups in large pair-count cables

Corroborated

Binder and super-unit colours can vary by manufacturer and by cable specification.

  1. Access Communications: Multi-pair telephone cable colour code (opens in a new tab)25-pair major/minor colours, tip and ring, binder groups up to 600 pairs
  2. Caledonian Cables: Telephone cable colour codes and make-up (opens in a new tab)25-pair tip and ring colours, binder group sequence and super-unit binders

Checked 9 Nov 2026

UK telephone sockets. BT colours.

Internal UK telephone extension wiring uses the first pairs of the same code, landed on numbered IDC terminals in the master and extension sockets.

Swipe the table sideways to see every column.

UK telephone socket terminal colours, current and older BT
TerminalUsual colour todayJobOlder BT colour (check)
1Not usedNot connected in normal wiring–
2Blue with white bandsSpeech and ringing (the line pair)Blue
3Orange with white bandsBell (ringing) wire for older phonesBrown, green on some
4White with orange bandsSpare, often connected for neatnessGreen, brown on some
5White with blue bandsSpeech and ringing (the line pair)Orange
6Not usedNot connected in normal wiring–

Check local rules The older BT column comes from a single hobbyist source that notes local variations. Always trace both ends of the cable rather than trusting colours on old wiring.

UK BT telephone socket colours (current)

Corroborated

Always check both ends: older and DIY wiring often ignores the usual colours.

  1. TLC Direct: Telephone wiring (technical guide) (opens in a new tab)UK socket terminals 2, 3, 4, 5 and usual BT cable colours
  2. Telephones UK: Wiring info (opens in a new tab)Modern socket pin colours and older pre-1980s BT colours with conversion variations

Checked 9 Nov 2026

Older BT colours (pre-1980s)

Check local rules

Only one hobbyist source was found and it records local variations. Treat as a guide only.

  1. Telephones UK: Wiring info (opens in a new tab)Modern socket pin colours and older pre-1980s BT colours with conversion variations

Checked 9 Nov 2026

Fibre colours. Twelve, then repeat.

TIA-598 gives a 12-colour sequence used for both buffer tubes and the fibres inside them. Count the tube first, then the fibre within that tube.

123456789101112Tubes outsideFibres inside
  1. 1BlueBL
  2. 2OrangeOR
  3. 3GreenGR
  4. 4BrownBR
  5. 5SlateSL
  6. 6WhiteWH
  7. 7RedRD
  8. 8BlackBK
  9. 9YellowYL
  10. 10VioletVI
  11. 11RoseRS
  12. 12AquaAQ

Memory aid: Blue, Orange, Green, Brown, Slate, White, then Red, Black, Yellow, Violet, Rose, Aqua. The first five match the 25-pair minor colours.

Fibre number lookup

Enter a fibre count number and how many fibres each tube holds. The wheel highlights the tube (outer ring) and fibre (inner ring).

Fibre 37 is in tube 4, position 1 in that tube.

Tube 4Brown
Fibre 1 of 12Blue

Beyond twelve.

The 13th to 24th tubes or fibres repeat the sequence with a black stripe, black dashes or a black tracer. The repeated black item needs a different mark.

How positions 13 to 24 are marked for tubes and for fibres
PositionAs a tubeAs a fibre in a 24-fibre tube
13Blue with black stripeBlue with black stripe or dashes
14Orange with black stripeOrange with black stripe or dashes
15Green with black stripeGreen with black stripe or dashes
16Brown with black stripeBrown with black stripe or dashes
17Slate with black stripeSlate with black stripe or dashes
18White with black stripeWhite with black stripe or dashes
19Red with black stripeRed with black stripe or dashes
20Black with yellow stripeNatural (uncoloured) with black marks
21Yellow with black stripeYellow with black stripe or dashes
22Violet with black stripeViolet with black stripe or dashes
23Rose with black stripeRose with black stripe or dashes
24Aqua with black stripeAqua with black stripe or dashes

Groups beyond 24 use other stripe colours that differ between manufacturers (red and orange are both used for 25 to 36). Large tubes may also be split into bundles with coloured binder threads. Always confirm with the cable datasheet.

TIA-598 fibre and tube colour sequence

Verified

Sequence confirmed by cable manufacturers Corning and Prysmian and by the Fiber Optic Association.

  1. Fiber Optic Association: Fiber optic colour codes (opens in a new tab)TIA-598 12-colour sequence, striped repeats, jacket colours by fibre type and connector colours
  2. Corning: Optical fiber color codes (AEN 29) (opens in a new tab)12-colour sequence; fibres 13 to 24 repeat with a black tracer; fibre 20 exception
  3. Prysmian: Color code guide for fiber optic specifications (opens in a new tab)12-colour sequence; units 13-24 black stripe (black unit yellow stripe); 24-fibre tube marking methods

Checked 9 Nov 2026

Marking beyond 12 fibres or tubes

Corroborated

Groups 13 to 24 use a black stripe or dashes on every source. Marking for groups beyond 24, and the colour used on a repeated black item, varies between manufacturers.

  1. Fiber Optic Association: Fiber optic colour codes (opens in a new tab)TIA-598 12-colour sequence, striped repeats, jacket colours by fibre type and connector colours
  2. Corning: Optical fiber color codes (AEN 29) (opens in a new tab)12-colour sequence; fibres 13 to 24 repeat with a black tracer; fibre 20 exception
  3. Prysmian: Color code guide for fiber optic specifications (opens in a new tab)12-colour sequence; units 13-24 black stripe (black unit yellow stripe); 24-fibre tube marking methods

Checked 9 Nov 2026

Jacket colours. Spot the fibre type.

Indoor patch cords and premises cable are coloured by fibre type under TIA-598. Outdoor cable is usually black whatever is inside, so read the legend printed on the sheath.

OM1 62.5/125
OM162.5/125 multimode
Jacket
Orange
Connector
Beige
OM2 50/125
OM250/125 multimode
Jacket
Orange
Connector
Black
OM3 50/125
OM350/125 laser-optimised
Jacket
Aqua
Connector
Aqua
OM4 50/125
OM450/125 laser-optimised
Jacket
Aqua (violet in parts of Europe)
Connector
Aqua
OM4 Regional
OM4Regional violet option
Jacket
Heather or erika violet
Connector
Aqua or violet
OM5 50/125
OM550/125 wideband
Jacket
Lime green
Connector
Lime
OS1 / OS2 9/125
OS1 / OS29/125 singlemode
Jacket
Yellow
Connector
Blue (UPC) or green (APC)

On-screen colours are approximate. Violet OM4 is a regional practice, mainly in the UK (heather violet) and mainland Europe (erika violet); TIA-598 itself keeps OM4 in aqua.

Jacket colours by fibre type

Corroborated

TIA-598 jacket colours for premises cable. Outdoor cable is usually black whatever the fibre.

  1. Fiber Optic Association: Fiber optic colour codes (opens in a new tab)TIA-598 12-colour sequence, striped repeats, jacket colours by fibre type and connector colours
  2. Black Box: Understanding fiber optic cable and connector colors (opens in a new tab)Jacket colours OM1 to OM5 and OS2; connector colours; violet for OM4 used by some makers but not adopted industry-wide

Checked 9 Nov 2026

Violet OM4 jackets

Corroborated

A regional and manufacturer practice, mainly in Europe. Aqua is still the TIA-598 colour for OM4.

  1. Belden: Differentiating between OM3 and OM4 (opens in a new tab)OM4 traditionally aqua; violet OM4 (heather violet in the UK, erika violet in mainland Europe)
  2. Black Box: Understanding fiber optic cable and connector colors (opens in a new tab)Jacket colours OM1 to OM5 and OS2; connector colours; violet for OM4 used by some makers but not adopted industry-wide

Checked 9 Nov 2026

Connector colours. Blue, green, beige, aqua.

Connector bodies, boots and through-adapters follow the fibre type, and for singlemode they also show the polish. Mixing them causes loss and can damage end faces.

Singlemode UPCFlat-polished singlemode. The everyday singlemode connector.
Singlemode APCAngled 8° polish for low back-reflection: PON, FTTH, video and many carrier links.
OM1 multimode62.5/125 multimode.
OM2 multimode50/125 multimode.
OM3 / OM4 multimodeLaser-optimised 50/125.
OM5 multimodeWideband 50/125.
UPCAPC 8°

Never mate green with blue. An APC connector is polished at 8° so reflections are sent out of the core. Pushing it into a UPC connector leaves an air gap at an angle, causing high loss and possible end-face damage. If an adapter is green, both connectors should be green.

Connector colours

Corroborated

Colours apply to connector bodies, boots and adapters. Never rely on colour alone to tell APC from UPC: check the endface.

  1. Fiber Optic Association: Fiber optic colour codes (opens in a new tab)TIA-598 12-colour sequence, striped repeats, jacket colours by fibre type and connector colours
  2. Black Box: Understanding fiber optic cable and connector colors (opens in a new tab)Jacket colours OM1 to OM5 and OS2; connector colours; violet for OM4 used by some makers but not adopted industry-wide
  3. Fluke Networks: What is an APC connector and how do I test it? (opens in a new tab)Blue bodies are UPC, green are APC with an 8 degree endface; UPC and APC cannot be mated

Checked 9 Nov 2026

Work safely. Light, glass and power.

Data cabling is low voltage, but it is rarely the only thing in the ceiling void. These are the hazards that catch people out.

Never look into a fibre

Network lasers work in the infrared, so a live fibre looks dark. Do not look into a fibre end or a connector, and never through a microscope, until a power meter or live-fibre detector has shown it is dark. Point visual fault locators away from your face.

Treat offcuts as glass

Cleaved fibre ends are tiny, sharp and almost invisible. Wear safety glasses, put every offcut in a marked sealed container, keep food and drink away from the work area and wash your hands before touching your eyes.

PoE puts power on the cable

PoE cables are live while the switch port is on. High-power PoE warms cable bundles, so follow the cable maker’s advice on bundle size and avoid large, tightly combed bundles. Use connectors rated for unplugging while powered.

Keep data apart from mains

Under BS 7671, data (Band I) and mains (Band II) circuits may only share containment if every cable is insulated for the highest voltage present, or they run in separate compartments or separate containment. BS EN 50174-2 adds separation distances that depend on how the cables are screened and contained. Where data and power cables must cross, protect the crossing, and never share a compartment with exposed live terminals.

Fibre laser and glass safety

Corroborated

Safety guidance from the Fiber Optic Association and Fluke Networks.

  1. Fiber Optic Association: Fiber optic safety (opens in a new tab)Infrared light is invisible; check with a power meter; fibre shard handling; chemicals
  2. Fluke Networks: 5 vital safety rules for working with fiber optic cables (opens in a new tab)Never look into the end of a fibre; contain glass fragments; work near power

Checked 9 Nov 2026

Separating data cables from power

Corroborated

Principles only. Take distances from BS EN 50174-2, BS 7671 and the cable maker.

  1. Voltimum / NICEIC: Installation of Band I and Band II circuits (opens in a new tab)BS 7671 Regulation 528.1 segregation methods and 528.2 proximity to other services
  2. Professional Electrician: Networking data cables, the key requirements (opens in a new tab)BS 7671 528.1 shared wiring systems; support of data cables in fire
  3. Mayflex: What are separation distances? (opens in a new tab)EN 50174-2 separation between telecoms and LV power cabling depends on what separates them

Checked 9 Nov 2026

Run the numbers. Then learn the trade.

Check PoE power budgets, voltage drop and cable sizing with the Tradefox electrical calculators.

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