Sorting Transformers
If you KNOW that the primaries are 120v, and you know which leads the primaries are, then just hook the primary up to 120v and use your meter to measure the various secondary voltages.
As to the color codes, first the obvious: same colors are the same winding. Duh. But, I had to start there just in case ....
Transformer color codes were pretty consistent and standardized in the 1940s, 50s and 60s, but have gone a little haywire since then, especially if you have Asian imports. Here's the old color code, or as much of it as I can remember.
Black is the primary; black with a stripe is likely a tap on the primary for an alternate voltage, such as 110v vs. 120v. Typically, any solid color is one end of a winding, while that color with a stripe (usually a yellow stripe) is the center tap.
Red is the high voltage winding, red-yellow the center tap. Be careful of this winding when you're measuring voltage, because if it's a transformer from some older tube equipment, the voltage across the red leads could be as high as 500 or 600 volts!
Green is the 6.3v heater winding on an old tube transformer.
Yellow is the 5.0v rectifier heater winding on an old tube transformer. This winding is well-insulated to withstand hundreds of volts since it will be connected directly to the B+ line.
Brown is another 6.3v heater winding, usually with a lesser current capability.
Orange is sometimes a higher voltage secondary, but not as high as the red leads. That's a rare color to find on the older transformers.
You may have four primary leads, a pair for two independent primaries. This is for a dual voltage transformer. Typically, each primary winding is 120v. Put them in parallel for 120v operation and maximum rated current from the secondaries; put them in series for 240v operation and maximum rated current from the secondaries. Using just one of the 120v primaries for the primary and the other 120v primary as a 120v secondary can be done, but you'll have only half of the original total volt-amps (sorta like watts) available from the secondaries, including the new primary-being-used-as-a-secondary.
Now, most of this goes out the window if you have a load of Asian import transformers. Even the primaries may have weird colors.
In any case, with the transformer connected to nothing, you can use your ohmmeter to determine which windings are connected together, which are center taps, etc.
Dean