First there is no NEC standard for color coding phase A may be Red in one building and blue in another.
For that matter phase A will likely be Brown and Black in the buildings I work in.
Brown for 480 volt systems and Black for 208 systems, again those colors are not standard they are more of a habit in this area.
The NEC requires this.
408.3(E) Phase Arrangement. The phase arrangement on 3-phase buses shall be A, B, C from front to back, top to bottom, or left to right, as viewed from the front of the switchboard or panelboard. The B phase shall be that phase having the higher voltage to ground on 3-phase, 4-wire, delta-connected systems. Other busbar arrangements shall be permitted for additions to existing installations and shall be marked.
But, when I connect to the power company (or they connect to me) I do not know which conductor is truly A.
Some have said any connection that results in clockwise rotation is correct and that may be so but I have never seen that written in a code or standard.
So once we land the conductors at the service disconnect we do not change from that point on except as needed at motor terminals.