I assume that you are in the situation with two voltages in the same building, probably 120/208V and 277/480V. If that is the case then:
200.6 Means of Identifying Grounded Conductors.
(D) Grounded Conductors of Different Systems.
Where grounded conductors of different systems are installed in the same raceway, cable, box, auxiliary gutter, or other type of enclosure, each grounded conductor shall be identified by system. Identification that distinguishes each system grounded conductor shall be permitted by one of the following means:
(1) One system grounded conductor shall have an outer covering conforming to 200.6(A) or (B).
(2) The grounded conductor(s) of other systems shall have a different outer covering conforming to 200.6(A) or 200.6(B) or by an outer covering of white or gray with a readily distinguishable colored stripe other than green running along the insulation.
(3) Other and different means of identification as allowed by 200.6(A) or (B) that will distinguish each system grounded conductor.
The means of identification shall be documented in a manner that is readily available or shall be permanently posted where the conductors of different systems originate.
If that is the case you need to decide which rule is more important: not taping small conductors or identification of voltages. I would go for 200.6(D) id the voltages. NOTE: if you are taping the neutral gray, would you not also tape the hot wire?
As a matter of curiosity what sort of installation has 277V and NM cable?