though I believe that by the 1971 edition specific multiwire color coding had been reduced to an unenforceable “suggestion”/fine-print note.
Yep, I'm looking at the 1971 NEC now:
210-5(c) Ungrounded conductor. Where installed in raceways, as open work or concealed knob-and-tube work, the ungrounded conductor shall be identified by any color other than as specified in (a) and (b) above. All ungrounded conductors of the same color shall be connected to the same ungrounded feeder conductor and the conductors for systems of different voltages shall be of different colors.
Exception: As permitted in Section 200-7.
It is recommended for a basic single wiring system that the following colors be used: 3-wire circuits, 1 black, 1 white and 1 red; 4-wire circuits, 1 black, 1 white, 1 red, and 1 blue.
There's a bar down the whole of 210-5(c), so something there was changed from the previous edition.
Roger, SafetyGem,
I should have mentioned that orange is mentioned in that 1971 code:
200-6(c) Where on a 4-wire delta-connected secondary, the midpoint of one phase is grounded to supply lighting and similar loads, that phase conductor having the higher voltage to ground shall be orange in color or be indicated by tagging or other effective means at any point where a connection is to be made if the neutral conductor is present.
A bar indicating a revision extends across the two lines which I've highlighted above. Maybe this was the start of orange, unless something else was changed.
