|Below are some of the most widely distributed
manufacturers with their prefered color schemes. For lack of a better
system, the wires will be designated by letters corresponding to the coil
and end from which they originate
A = Neck-most coil, left side
Note that several manufacturers are not mentioned here:
Fender doesn't seem to have any after-market humbuckers that I could find.
EMG pickups are anomolous in that they do not have traditional coils, let alone 4 conductors. In fact, only their model 89 pickup can be "tapped," and that's by a specific scheme of more wires than is conventionally required.
If you see any brands I missed, please email me.
Thankfully, single coil pickups are fairly straight forward. In general, the black wire is the ground side of the coil. The other color can be almost anything else. On Fender guitars, two of the non-ground leads are white, but the one from the middle pickup is yellow. This is to designate that pickup as different. Specifically, it is reverse-polarity and is reverse-wound. This makes it hum-canceling when combined with either of the other two pickups.