200.6
(A) Sizes 6 AWG or Smaller. An insulated grounded conductor
of 6 AWG or smaller shall be identified by one of the following
means:
(1) A continuous white outer finish.
(2) A continuous gray outer finish.
(3) Three continuous white or gray stripes along the conductor's
entire length on other than green insulation.
(4) Wires that have their outer covering finished to show a
white or gray color but have colored tracer threads in the
braid identifying the source of manufacture shall be
considered as meeting the provisions of this section.
(5) The grounded conductor of a mineral-insulated, metalsheathed
cable (Type MI) shall be identified at the time
of installation by distinctive marking at its terminations.
(6) A single-conductor, sunlight-resistant, outdoor-rated cable
used as a grounded conductor in photovoltaic power
systems, as permitted by 690.31, shall be identified at the
time of installation by distinctive white marking at all
terminations.
(7) Fixture wire shall comply with the requirements for
grounded conductor identification as specified in 402.8.
(8) For aerial cable, the identification shall be as above, or by
means of a ridge located on the exterior of the cable so as
to identify it.
(B) Sizes 4 AWG or Larger. An insulated grounded conductor
4 AWG or larger shall be identified by one of the following
means:
(1) A continuous white outer finish.
(2) A continuous gray outer finish.
(3) Three continuous white or gray stripes along the conductor's
entire length on other than green insulation.
(4) At the time of installation, by a distinctive white or gray
marking at its terminations. This marking shall encircle
the conductor or insulation.