49 CFR § 236.76
Tagging of wires and interference of wires or tags with signal apparatus
November 18, 2020
Each wire shall be tagged or otherwise so marked that it can be identified at each terminal. Tags and other marks of identification shall be made of insulating material and so arranged that tags and wires do not interfere with moving parts of apparatus.
[49 FR 3384, Jan. 26, 1984]