We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Harry Bloomfield
saying something like:

I'm surprised no one uses those white slide on tags as used in panels,
with letters/numbers printed on them in black. Two tags marked S and W,
to make up SW for switch wire -would leave no one in any doubt.

For a wire which will, in all probability, never be looked at again? Get
real.
Such things are useful in control panels for plant, where the opening of
the lid more than once and someone rooting around fixing a fault is very
likely during the lifetime of the equipment.