The colors you see in CAT5 wiring or the 4-way station cable commonly used for internal phone wiring these days do actually use the first few color pairs of the larger overall system.
It's not really that difficult to learn. There are two sets of base colors for each side of the line, viz.:
Tip: white, red, black, yellow, violet
Ring: blue, orange, green, brown, slate
If you can memorize those two sequences, you can work out the colors for any pair quite easily.
The first five pairs use white as the base tip color with each of the ring colors in turn, thus pair #1 is white/blue (tip) and blue/white (ring), pair #2 is white/orange (tip) and orange/white (ring) etc.
For the next five pairs, you just repeat the sequence but with red in place of white. The next five then all have black as the base tip color, and so on. By the time you've worked with it a while, you just mentally "look up" the color for a given pair without having to count the colors.
For larger cables, the wires are bundled into groups of 25 pairs each and each bundle is individually identified.
A particular line may well run through several different pairs on its way to somebody's house. For example, it might come out of the CO building on a black/green pair, then go from a main distribution point to a smaller cabinet on a red/blue pair, then from there to a pole junction box as a white/brown pair. That's why the records of lines are so important!
The older-style phone cables used solid colors instead of the banded insulation found today. Pair #1 consisted of just a plain white wire (tip) and a plain blue wire (ring) twisted together. #2 would then be white and orange, and so on. So in say a 10-pair cable you'd actually have 2 blue wires, 2 orange, 2 green, 2 brown, 2 slate, 5 white, and 5 red. You try not to untwist the pairs, otherwise you're in for some real fun......
[This message has been edited by pauluk (edited 12-17-2002).]