is there any code violation to mark #10AWG wire in 3 phase by using a color tape.
Example I'm using 3 phase to run the heater and want to tape white wire blue?
In general, if the NEC requires a color for a specific conductor purpose within the circuit, it requires a factory finish to establish this color for #6 and smaller. #4 and larger can usually be taped any color for any application. I have yet to understand why it is incorrect to tape the small conductors, as I see no practical consequence to it. Mostly the academic consequence of the fact that it could be the basis for failing an inspection.
The NEC doesn't require the phase marking of the ungrounded AC wires, provided that voltage systems aren't mixed in the same wiring structure. Any color of wire that is not already reserved, is permitted. White and gray are reserved, green is reserved, and in applications where there would be a high leg, orange is reserved. The way I interpret this, is that if you are going to remark the wire that is #6 and smaller, it has to start with a factory finish that would be acceptable in that particular application. So starting with a white and taping it blue, would not be allowed. But starting with all black, and taping it the respective colors, would be acceptable, provided that you still use white/gray and green where specifically required.
The NEC requires marking of grounded conductors (white or gray), equipment grounding conductors (bare, green, or green w/ yellow stripe), high legs (orange), and polarities in DC (red and black).
