Why Do Colors Matter?

Ethernet cables are the backbone of any wired network, connecting your computers, routers, and gaming consoles to the internet. Inside that cable, 8 tiny copper wires are twisted into 4 pairs. Each pair has a specific job, and the color code is the universal language that tells you which wire goes where. Getting it right means a fast, reliable connection. Getting it wrong means a network that doesn’t work.

This guide will explain the two standards—T568A and T568B—with clear pictures, tables, and simple steps.

The Two Color Code Standards

There are two approved wiring standards: T568A and T568B. They are very similar, but the order of the colored wires is different.

Key Fact: For a standard straight-through cable (used to connect different devices, like a computer to a router), both ends must use the same standard (A-A or B-B). For a crossover cable (used to connect similar devices, like computer-to-computer), one end is T568A and the other is T568B.

T568A Color Code Table

When holding the RJ45 plug with the clip facing down and the copper pins facing you, the wire order from left to right (Pin 1 to Pin 8) is:

Pin #Wire ColorPair #Function
1White/GreenPair 3Transmit+
2GreenPair 3Transmit-
3White/OrangePair 2Receive+
4BluePair 1Unused
5White/BluePair 1Unused
6OrangePair 2Receive-
7White/BrownPair 4Unused
8BrownPair 4Unused

*Simple Memory Tip for T568A: “White-Green, Green, White-Orange, Blue, White-Blue, Orange, White-Brown, Brown.”*

T568B Color Code Table

This is the most common standard in North America and for most commercial and residential networks. The pinout is:

Pin #Wire ColorPair #Function
1White/OrangePair 2Transmit+
2OrangePair 2Transmit-
3White/GreenPair 3Receive+
4BluePair 1Unused
5White/BluePair 1Unused
6GreenPair 3Receive-
7White/BrownPair 4Unused
8BrownPair 4Unused

*Simple Memory Tip for T568B: “White-Orange, Orange, White-Green, Blue, White-Blue, Green, White-Brown, Brown.”*

Real-World Usage: Which Standard Should You Use?

  • Use T568B: This is the safe, default choice for almost all situations. It’s the most widely used standard. If you’re wiring a home or office, use T568B on both ends for your straight-through cables.
  • Use T568A: This is required for some government installations and is more common in residential telephone wiring (though less so now). It’s also used for the “A” end of a crossover cable.
  • The #1 Rule: Be Consistent. Pick one standard (we recommend T568B) and use it for everything in your installation. This prevents confusion and ensures all your cables are interchangeable.

Other Important Aspects

  • Cable Categories (Cat5e, Cat6, Cat6a, Cat8): The color codes are the same! The difference is in the cable’s construction, shielding, and maximum speed/distance.
  • Solid vs. Stranded Core:
    • Solid: Used for in-wall installations (patch panels, wall jacks). Less flexible but easier to punch down.
    • Stranded: Used for patch cables (connecting devices). More flexible and resistant to breaking from repeated bending.
  • Shielded (STP) vs. Unshielded (UTP): Most cables are UTP. Shielded cables (F/UTP, S/FTP) have extra foil or braiding to reduce electrical interference, crucial in industrial settings.

FAQ Section

Q: What is the most common Ethernet color code?
A: T568B is the most common and recommended standard for new installations.

Q: Can I use T568A on one end and T568B on the other?
A: Yes, but this creates a crossover cable, used for connecting two similar devices directly. For standard device-to-router connections, use the same standard on both ends.

Q: What happens if I mix up the wires?
A: The cable will likely fail or cause slow, unreliable network speeds. A cable tester is essential to catch errors.

Q: Are Cat5e and Cat6 color codes the same?
A: Yes, the T568A and T568B color codes are identical for all standard Ethernet cable categories (Cat5, Cat5e, Cat6, Cat6a, Cat7, Cat8).