210.4(D):
Quote
Identification of ungrounded conductors. Where more than one nominal voltage system exists within a building, each ungrounded conductor of a multiwire branch circuit, where accessible, shall be identified by phase and system. This means of identification shall be permitted to be by a separate color coding, marking tape, tagging, or other approved means and shall be permanently posted at each branch-circuit panelboard.
Ah... I guess that covers it. So this would be a violation of 210.4(D) unless black/red/blue was used consistently throughout the building for 277 and some other colors used for 120.

And I would imagine that a scribbled note on the box cover doesn't count as "other approved means," especially as it's unlikely to be repeated at the panelboard. [Linked Image]

As a matter of interest, what methods are considered acceptable othan the color-coded insulation, colored phase tape, or tags with appropriate legends on them?