I've been inside plenty of machines where once the power cord ends inside the machine, every wire is black. You get lucky if they are numbered!
Most of my work these days is HVAC. Lots of 120V motors use a yellow or purple for their neutral, just like the same brand 240V motors use for the "common" hot.
But you raise an interesting point. Since you are not just rewiring, but redesigning the fixture, it's existing UL-Listing, if any and applicable, would be void, wouldn't it? That might matter. Would the new LED lamps, by virtue of their instructions, bring their Listing to the newly redesigned fixture?
Regardless, I foresee lots of these fixtures in places that change ownership, and the new people try to put standard fluorescent tubes in, for whatever reason, and wonder why they don't work.
