How about........ (key word 'grounding')
Article 100 Definitions:
Grounded. Connected to earth or to some conducting body that serves in place of the earth.
Grounded Conductor. A system or circuit conductor that is intentionally grounded.
Grounding Conductor. A conductor used to connect equipment or the grounded circuit of a wiring system to a grounding electrode or electrodes.
The later mixes the words "grounding" and "grounded" in a single definition that actually referes to two separate terms used elsewhere in the NEC.
What a conundrum!(a : a question or problem having only a conjectural answer b : an intricate and difficult problem)
Since there is no clear answer to be found in the NEC, but the words "grounding conductor" are used in reference to (A) the "grounding electrode conductor", which never specifies an identification in reference to color, and (B) the " equipment grounding conductor" which specifies an identification in reference to color (green),we are left to wonder what color if any, we are to use.
It would seem logical based on the above definitions to choose green since one is specified and one is not.