I'm not sure anyone claims there was a Red 2 pyro? Can't recall.
Just saying it again, there wasn't a special effort made to match the colour schemes between pyros and heros. Red 1 pyro and hero match better than Red 3 pyro and hero, but that's an exception, not a rule.
The Red 3 hero in the Archives is the one built for Star Wars. It's seen in a clear, large top view in The Art of Star Wars. There's an underside view taken in the same shoot, on Behind the Magic.
The model's underside WAS MODIFIED for
ESB, as it was given landing gear to act as a stand-in for Red 5.
The pics you ask for are all on the various X-wing threads. Recommended reading.
That is no myth, again, the photograph is here on the forum.