So most all 1928 and 1929 cars were not originally painted black from the factory?
Not the bodies, only the fenders, splash apron, etc., beneath the body.
Andalusite Blue was available for many body styles in '28/'29. It is a very dark blue, almost black. It looks black when not well lit.
Have a paint shop do a computer scan of the existing paint that want to match.
Do a test spray with that to confirm the match.
No paint code or formula will match existing old, aged paint. Better to match what you have.