I had some spare 10/3 NM cable from which I repurposed the black, white, and bare wires and ran through conduit. There's a circuit junction nearby that doesn't have a ground and isn't spliced inside a j-box. The line side is just a hot and a neutral. The load side goes to a light outside and is 14/2 NM cable. The spare red wire from the 10/3 NM, can I use that to ground the 14/2 NM and just identify it as a ground with green electrical tape every few feet?
The portions of the NEC I've read pertain to identifying the neutral but I can't find something that references the coloring of an earth/grounding wire.