The lost art of telephony, as lamented on this very forum recently. Back in the old days, everyone used the same convention for colors, and there were no peckerhead civilians allowed in the closets. We could walk into a closet that we had never seen before, and know exactly what the previous ten guys had done.
I was able to install and repair 4 gazillion 1A2 telephones over the years with triple-pair (B,O,G) for station features, Blue/Yellow for CO lines, and solid color red, green and black, single leads stolen from quad wire when spools were too far away, for ringer matrix, CMB, relays, etc. Same color codes as used by the manufacturer on KTU's and PBX equipment plates.
Red = power, Black = ground, Green = interconnection between relays.
Yellow/blue for buzzers.
Red/white for special ckts, such as alarms, tie-trunks, pushbutton on the secretary's desk to let the boss know that his wife just got off the elevator, and boy, does she looked pissed!
