In the Pelican Parts catalog you can find downloadable, free, color-coded wiring diagrams for the early Porsches and the 1975. I downloaded them a week or so ago but can't find the exact link right now or would have included it. Don't give up! They are there and are very useful.
Ah, here they are:
http://www.pelicanparts.com/911/911_parts/911_electrical_diagrams.htm
Tom