Yesterday I mentioned in passing that we had a colour scheme for network cables, at least in our machine room and some wiring closets. To illustrate our environment, here's the cable colours we currently use:

(I should note that this is for the cables themselves, not for the cable shrouds at the end of the cable. Our usual habit is to make the cable shrouds the same colour as the cable, but we don't worry about it too much.)

A couple of research groups also use some of these colours to keep their own network setups straight; I believe that black and yellow are 'shared' colours, and there is also someone using purple cables for something. The shared colours don't cause confusion because they're in completely separate places; our black and yellow wires only get used in one small area of our machine room.

(But where they get used they are very handy at keeping straight which iSCSI network is which and making sure that no one ever mistakes an iSCSI network or switch for anything ordinary.)

We're not very big on labeling our cables unless they're really important or unusual. Our experience with things like cable labels is that they are like comments in source code; they're fine until things start changing and then they never get updated and become actively misleading. If we're not going to be able to trust cable labels, it's better not to have them at all.