Network Cable Color Code: T568A vs T568B, RJ45 Pinout & PoE Guide

“The color chart is not there to help the operator memorise eight wires. It is there to protect pair integrity. If you lose that, you can still pass pinout and still ship a bad cable.”

Buyers often confuse network cable color code with mains wiring colors or generic harness identification. They are different systems. Our Australian wire color guide covers AS/NZS and control wiring conventions; RJ45 color code is specifically about how the four twisted pairs land on the eight pins inside a modular plug or jack.

That matters whether you are building office patch cords, structured cabling for data infrastructure, or rugged industrial RJ45 cable assemblies for PLCs and machine Ethernet.

T568A vs T568B: what actually changes

T568A and T568B are both valid. Electrically, neither is faster. The only difference is which pair lands on pins 1-2 and which lands on pins 3-6. In T568A, the green pair sits on pins 1-2 and the orange pair sits on pins 3-6. In T568B, that arrangement is reversed.

In practice, T568B is more common in commercial patch leads and legacy North American infrastructure, while T568A is still preferred in some government and residential environments because it is backward-compatible with one older USOC pairing convention. In Australia, the most important rule is consistency: choose one approved scheme for the site, cabinet, or product family and keep both ends aligned unless the design intentionally calls for a crossover.

How manufacturers read the RJ45 pinout

When production teams talk about “network cable color code,” they are really talking about controlled pair routing. Pins 1-2, 3-6, 4-5, and 7-8 are assigned to four twisted pairs. If one conductor is moved outside its pair, near-end crosstalk and return loss worsen because the geometry assumed by the channel standard no longer exists.

This is why factory-made patch cords outperform improvised field leads. A production build uses the correct plug for stranded or solid conductor, checks conductor insertion depth, measures crimp height or plug seating where relevant, and often validates the assembly beyond continuity when the application is critical. For higher-speed or shielded assemblies, that validation aligns with the same signal-integrity discipline covered in our high-speed cable assembly guide.

“If an operator trims the jacket too short or untwists a pair just to make the colors line up more neatly, the cable may look cleaner and perform worse. Inspection has to reward electrical discipline, not cosmetics.”

Straight-through vs crossover vs rollover

The first question is not “A or B?” It is “what cable behaviour does the equipment need?” Most modern network assemblies are straight-through. Crossover and rollover cables still exist, but they are special-purpose builds and should be labelled clearly to avoid accidental deployment.

If your program still uses crossover or console variants, make that explicit in the drawing, label, packout, and test instruction. A cable that “looks RJ45” is too easy to mis-pick in production or maintenance if the documentation is vague.

PoE, shielding, and industrial Ethernet risk

PoE does not require a new color code, but it does raise the consequence of a bad termination. Higher current means higher contact heating. In bundled cables, elevated temperature can increase insertion loss and reduce margin on long channels. In harsh environments, that is often compounded by vibration, oil mist, cabinet heat, and imperfect grounding.

For OEM builds, the cable review should therefore include category, conductor construction, plug rating, plug-to-cable compatibility, shield continuity, and whether the assembly is part of a broader multi-pair or mixed-signal routing strategy. A shielded cable only helps if the complete interconnect path is designed correctly.

“PoE exposes quality shortcuts fast. A connector with marginal blade contact might survive data-only service for months and then heat up immediately when current is added. That is why we review Ethernet as an electrical assembly, not just a network accessory.”

Inspection checklist for production-ready network cables

A reliable Ethernet cable assembly needs more than “pins light up.” The inspection plan should separate visual workmanship, dimensional control, electrical validation, and where needed, channel or application-specific testing.

Common wiring mistakes buyers should catch early

FAQ