Striped Wire Trick
I found myself needing a white wire with a black stripe.  The local auto parts stores didn't have any.  So, I got out a Magic Marker (permanent ink marker) and put a stripe on a white wire.  While this wouldn't resist solvents or UV very well, those shouldn't be a problem for the application I had.  Of course there are other color markers that could be used in the same way (and there may be some vinyl dyes that would work even better).

Rich Arimoto