Is it code legal to mark neutrals that actually are neutral?
Identifying Multiple Neutrals To Its Own Branch Circuit
The best way to do this is to use wire numbering stick-on labels, which solves the whole &quot;what color can I use&quot; question.  Each current carrying conductor of a single branch circuit is tagged with the SAME number. For example, all the  current carrying conductors of the branch circuit &quot;kitchen lights&quot; are tagged with the number &quot;5&quot;.

To make even better, the numbering system corresponds to the breaker location.
Here is a pic of a panel I did recently.