I'm losing faith in the Code day by day. If this were a new instalation, yes, use the proper color. But seeing as how the old white wire is cemented in, then you are faced with removing and replacing the compound as well as replacing the wire. Maybe $50 or $100 bucks to satisfy some stupid technical rule [in this case] versus 5 cents worth of tape.
And, as is pointed out, the electricity doesn't care.
~Peter
It would be a lot more than $100. It could also wind up being a job to replace the conduit if the existing conductors cannot be removed (chico not properly installed and down in the 90, internal conduit corrosion that won't allow the conductors to come out).
In this case I would not hesitate to use the existing conductors if the insulation is OK and the
white wire did not feed anything else other than the pump motor.
As far as the e-stop, if it is properly installed, it is breaking the neutral now and would still break the neutral changed to a hot. I would also trace the conductor through each box back to the panel and re-identify the white all the way back.
I would think a reasonable inspector may not make a big deal about this, what say you inspectors? Am I wrong?