I used as described by Shawn, "acetone very carefully" on a Schwinn phantom which had
been house spray painted blue.
The sprayed blue came off to reveal a red phantom. The original red was faded in parts.
I bought it at a low price and also because it was a complete bike with original parts.
I own several originals and seen others who
own original Phantoms with original parts
that I can tell if the saddle, pedals, fenders are
original or reproduction parts.
Nothing wrong with repo parts as long as they don't advertise it as all original and asking a very high price when I know it's not all original.
The guy who sold me the painted phantom which was given to him by a late uncle...
had no use for it.
He described it as an old "peewee herman",
very heavy with no shifting speeds.
It was out in the back with no protection from the weather.
Luckily, I managed to salvage it before it rusted away.