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Color Codes for RJ-45 Ethernet Plug
Category 5E cable (Cat 5E) contains 4 twisted pairs of wires. Each pair has a solid color wire (Blue, Brown, Green, Orange) and a white wire with a colored stripe.

The pairs used for Cat 5E connections are orange and green. The other two pairs, brown and blue, are unused. The wiring shown below are for an RJ45 plug.

T-568A Wiring

Pin 1 white/green
Pin 2 green
Pin 3 white/orange
Pin 4 blue
Pin 5 white/blue
Pin 6 orange
Pin 7 white/brown
Pin 8 brown

Receive Data +
Receive Data -
Transmit Data +
Unused
Unused
Transmit Data -
Unused
Unused

T-568B Wiring

Pin 1 white/orange
Pin 2 orange
Pin 3 white/green
Pin 4 blue
Pin 5 white/blue
Pin 6 green
Pin 7 white/brown
Pin 8 brown

Transmit Data +
Transmit Data -
Receive Data +
Unused
Unused
Receive Data -
Unused
Unused

The T-568A scheme is supposed to be the standard for new installations, with T-568B as the alternative. However, the majority of data equipment and cables seem to be wired to T568B.

Straight-Through vs. Cross-Over
The patch cords that you generally use with your Cat 5E connections are wired "straight-through", which means that connectors on both ends of the cable are wired identically using the same T-568A or T-568B standards.

The only time you cross connections in Cat 5E is when you connect two Ethernet devices directly together without a hub or connect two hubs together. Then you need a "cross-over" patch cable, which crosses the transmit and receive pairs. The simple way to make a cross-over cable is to wire one end with the T-568A standard and the other with the T-568B standard.