The internal parts of a generator are outside the scope of the NEC but once it leaves the generator it must comply with the NEC.
As Dave has pointed out with his post of 110.15 of the NEC if a color is used to identify the high leg it MUST be orange or if one wanted they could put a tag on it that shows that it is the high leg.
marked by an outer finish that is orange in color or by other effective means.
The only other colors that are mandated by the NEC is white or gray for the grounded neutral and green or green with yellow strips for the equipment grounding conductor.
The ungrounded (hot) conductors can be any color that the installer chooses. It has been a standard of practice (SOP) throughout the country to use Brown Orange and Yellow for 480/277 but then if there is a transformer that steps this system down to a 240/120 delta system then the orange color cannot be used for the 480/277 as the high leg of the 240/120 will be required to have this orange color. If the high leg of the 240/120 is identified with a tag the 480/277 still can’t be orange as this color is set aside to identify the high leg. If the building does not have a system with a high leg and is supplied with only a 480/277 wye system then the use of the “BOY” is allowed although I strongly object to this SOP (standard of practice).
I have installed many of a system using the standard black color that the conductors of size 4 and larger comes in and identify the phases using marking stickers as Phase “A”, Phase “B”, and Phase “C” looking at the panel from the front from top to bottom, left to right, or front to back.
In the premises wiring system electricians are not allow to just choose which color they want to use to identify the high leg, neutral, or the equipment grounding conductors. These conductors are mandated as to what color is to be used by 110.15 for the high leg, 200.6 for the neutral, and 250.119 for the equipment grounding conductor.