UTP has 4 twisted pairs of wires, we'll now look at the pairs to see what colour codes they have:
As you can see in the picture above, the 4 pairs are labeled. Pairs 2 & 3 are used for normal 10/100Mbit networks, while Pairs 1 & 4 are reserved. In Gigabit Ethernet, all 4 pairs are used.
UTP CAT5, 5e & 6 cable is the most common type of UTP around the world ! It's flexible, easy to install and very reliable when wired properly.
There are two wiring standards for these cables, called "T568A" (also called "EIA") and "T568B" (also called "AT&T" and "258A"). They differ only in connection sequence - that is, which color is on which pin, not in the definition of what electrical signal is on a particular color.
Note that the odd pin numbers are always the white with stripe color (1,3,5,7). The wires connect to RJ-45 8-pin connectors as shown below:
Color Codes for T568B
Pin Color Pair Name
1 white/orange (pair 2) TxData +
2 orange (pair 2) TxData -
3 white/green (pair 3) RecvData+
4 blue (pair 1)
5 white/blue (pair 1)
6 green (pair 3) RecvData-
7 white/brown (pair 4)
8 brown (pair 4)
Pin Number Designations for T568A
The T568A specification reverses the orange and green connections so that pairs 1 and 2 are on the centre 4 pins, which makes it more compatible with the telecom voice connections. (Note that in the RJ-11 plug at the top, pairs 1 and 2 are on the centre 4 pins.) T568A goes