I noticed the same dark corrosion problem with the wires on my boat. The wires do appear to still work. But I suspect there is increased resistance and therefore higher power use.
I also noticed the difference in wire coloring. Turns out, if you uncover the wire harness from the control panel far enough, you will find that the colored wires end and labeled wires begin. Each wire will have a numbered tag on it. A corresponding tag will exist near the base of the mast. If you dont find this, you get the fun job of checking for continuity. Another source is the J30 website in the Articles of Interest section. There you'll find a set of wiring diagrams from a newer (later model) J30. The diagrams arent exactly correct for the older boats. But they are a help none the less.
Good Luck
