I've got a Cobolt colour detector. What I do with it to look at wires is to lay
the wire on top of my power supply. The supply is in a gray metal case so it
provides a pretty nutral background and I can often tell wire colors that way.
Tom
Tom Brennan KD5VIJ, CCC-A/SLP
web page http://titan.sfasu.edu/~g_brennantg/sonicpage.html