The code means nothing. It is simply a convenient way of assigning a two character ID for anything up to 260 wires. A two character ID is easy to inscribe on the heat shrink sleeve at each terminal using an indelible felt-tip pen. I use only four or five colours and my larger 8AWG cable only comes in red and black anyway. Assign colours however you like.
Heat shrink colour .
This is the heat shrink which covers the terminal to wire connection. I have red, blue, black and white. If there are, for instance, two red wires arriving at the same accessory you can give one a blue shrink and one a white shrink to differentiate them. Each wire will have the same colour shrink at its other end, wherever that may be. Wire size .