You may call the original painting a "myth" but I was there when it was originally unveiled at the Smithsonian in (I think) 1976 and studied it extensively. To me it appeared freshly painted and I believe one or more of the windows were painted over. Believe what you want but the color that was used to repaint it did not even match the original color; it was slightly more blue as compared to the more greenish original color.
If you compare photos from that time that have both the top of the saucer and the rest of the ship it seems pretty obvious that it was repainted (a different color no less).
This is entirely true. The model was repainted, save for the top of the saucer, prior to its first public exhibition at NASM.