My old boss use to work in a big factory here in northern NJ and they use to have many different frequency lines. ( I believe they did a lot of work for satellites)What they would do is make sure that the odd frequency wires were marked and labeled with different colors. (Like purple) This way they didn't get the 120/240 red, blue, black and the 277/480 Brown, orange, yellow mixed up with the 500 Hz which was purple.
