New to FABO

Both colors are used to denote hot wires.

Not sure what diagrams you are looking. The factory diagram identifies all of the circuits, colors, and wire gage. The '67 diagrams are not quite as good as 68 but still pretty good. For '67 the Barracuda diagrams are in the '67 Service supplement 67-25-6.
This should be a direct link to the 67 Barracuda Supplement which has the fastback and rally dash wiring diagram.
http://www.mymopar.com/downloads/servicemanuals/1967_Plymouth_Service_Manual_Supplement.zip
if not, its on this page Service Manuals – MyMopar

There's also pdf of the shop manual diagram by @1969383S in this post.
Make sure you get the '67. There are changes each year.

Diagram wire codes covered here

Off the top of my head, gages are powered directly from I terminal on the key switch.
The instrument lights are powered through the headlight switch, then to the 2 amp fuse in the box, and finally up to the connector on the instrument board.

Two corrections to the factory diagram noted here. The difference mostly being that the wire for the instrument lights goes to the steering column connector first after the fuse box.

One thing in common is the grounding. There was an additional ground for the instrument panel to help insure good grounding.

Loose end shown above connected to the bottom of the dash panel under the screw for the radio support bracket.


and
:welcome:
Appreciate the help. Won't be able to get back on it until the weekend. The M&H Electric harness came pre-built with all the connectors, including the OEM style fuse box, attached. It's my understanding they bought all the design prints and maybe the jigs for all the Plymouth models. They state it is the "base" harness and does not include wiring for some of the add ons that you could get. So far everything is there except the orange wires that are spliced at a 5 way joint. Think that is what I will have to figure out. Plymouth (and Chrysler in general) kept making wiring changes, even in the same model year. Head scratcher for sure. I thought the IVR3 would solve the problem but no such luck so.... back to tracing.
Thanks again, I will eventually conquer this (no matter how many times I have to remove the dash).