Telephone cable wire color code

Telephone and Data Wire Color Codes

In some cases it's as simple as removing a plug from a jack. Still, a basic understanding of how telephone wiring works is useful before attempting to make such a switch. Some readers may choose to skip this preliminary information, but if you do that you may be cheating yourself out of acquiring some useful knowledge that will almost certainly come in handy at some point in the future. Traditional telephone service is provided over a pair of wires.

25-pair color code

Virtually all telephone wiring installed in the past 50 years or so contains at least two pairs of wires, but that does not mean that all phone wiring is suitable for carrying two phone lines. In today's telephone wiring, each phone line is put on a pair that consists of a solid colored wire such as solid blue twisted together with a white wire. Usually this white wire will have a stripe of the same color as the solid wire of the pair so you would have a blue wire paired with a white wire with a blue stripe , so that you don't get the white wires mixed up.

Occasionally you'll see variations on this for example, the mostly "solid" wire will have a white stripe in it but you can usually tell what the pairs are, in part because the wires in each pair are twisted together inside the cable.

Phone wire color codes

In newer homes Cat 5 wire is almost always used for communications wiring — if not it will probably be at least Cat 3, which uses the same color coding "Cat" is short for "category", by the way. Cat 5 wire generally has four pairs, while Cat 3 may have a different number of pairs, generally anywhere from three to six. The primary pair, or "Line 1", is usually the blue and white with blue stripe pair.

If there is a "Line 2", it is usually placed on the orange and white with orange stripe pair. Line three is on the green pair, and line four on the brown pair if there is a fifth pair, it will be grey, or to use correct telephone company terminology, "slate".

This color coding scheme for multi-line telephone wiring has been used for years. It is VERY bad practice to split pairs that is, to use one wire from one of the twisted pairs, and another wire from another of the twisted pairs as a pair.

What do the yellow and black wires in a home telephone jack do?

For example, we've seen an online video where they actually told people to use the solid green wire and the solid orange wire to make a pair. We apologize for harping on this, but it boggles the mind that anyone would actually tell people to do this, given the potential for introducing electrical and radio frequency noise, as well as crosstalk into conversations. Keep the twisted pairs together — each line on its own twisted pair!

The outer jacket of this wiring may be blue, green, grey, beige, white, or occasionally some other color blue is apparently the most popular outer jacket color for Cat 5 wire these days.

Telephone color code

With telephone wiring, particularly if Cat 3 wire was used, the actual number of pairs in a cable may vary, but if standards were followed during the installation, the blue and white with blue stripe pair is always the primary phone line. In older homes, you may find a whole different scheme, called "quad" wiring, which contains four wires colored red, green, yellow, and black. The primary phone line is normally the red and green wires.

Sometimes you will find a second line on the yellow and black wires, but this is not good practice because, in quad cable, the wire pairs are not twisted together, which can and often does result in "crosstalk" between the two lines.


The pair twisted wire color code standard for telephones and other telecommunications is easy to understand when you get to know it. Planning your installation and using the correct pairs in the right order will help you stay organized and let you to keep track of what wire does what.

Twisted pair telecommunications cables come in a variety of sizes numbered in wire pair sets from 1 pair up to pairs and more all set up into 25 pair groups. By reading these two colors the base and the strip you can determine which wire pair out of the group of 25 wire pairs you have. The color code ends with the colors slate for the wire and violet for the strip. The color code has 25 different variations to mark 25 wire pairs separately after that the numbers repeat for the next group of 25 wire pairs. So, looking on the table below you will see that wire pair 26 starts with white and blue again repeating the color pattern for the next 25 pairs and ends with slate and violet just like the first 25 pairs.

Get to know the color code and use it to your advantage to simplify your installations and remove the guess work.