What is the basic telephone wiring setup in the home?
There seem to be all these colors and it's really confusing!
Telephone wiring is color-coded...
In a typical home, the telephone cables connecting your phones within you home contain four wires... red, green, yellow and black. They are used in pairs for each phone line you have. Repairmen in fact refer to the wires in terms of "pairs", so technically a standard four wire telephone line has two pairs.
LINE 1 uses the red-green pair. Line 2 uses the yellow-black pair. The cable is very small, as are the wires inside, and should not be confused with electrical wires, which are much larger. The wires themselves are almost hair-like, as opposed to electrical wires, which are fairly heavy and difficult to bend.
FYI, if purchase multiwire cable with 4 pair (8 colored wires) for four lines, the wiring convention is the same as above, with LINE 3 using BLUE + WHITE and LINE 4 using ORANGE + BROWN.
All telephones, residential telephone cable, jacks, connectors, etc., that you can buy today follow this wiring convention. ALL OF THEM!!
Why your wiring colors don't match my colors...
That, of course, does not mean that this is the situation you have in your home's wiring! If a homeowner has messed with the wires, you may find things a little jumbled up. I frequently find disconnected wires at phone jacks, whole runs of wire to telephone jacks disabled at the junction block, and reversed wiring.
In some multifamily dwellings and in older homes, the wiring may not follow the color conventions for modern jacks and telephony appliances. This is especially true in some condominiums, where large bundles of wires servicing more than one customer may pass through your unit! It makes sense, really. You can't have twenty wires serving ten units using four colors.
I know there is a basement warehouse somewhere that contains volumes of secret government information about these wiring codes, undoubtedly next to the remains of space aliens in Roswell. You, however, don't need to crack the wiring code.
You can determine the proper colors for your particular situation by simply observing what-goes-to-where. If you open up a telephone wall jack, and see that RED is connected to the BLUE-WHITE multicolored wire, make a written note of it so you will not get confused when reconnecting the new whatever later! So it's not really as complicated as it looks. Just follow the wiring conventions that are working, and you should have no problems!