How are guys matching factory paint ?

After my '65 Formula S was painted (I wanted factory original white) I found that the trunk latch/catch still had the original paint. Something inside the trunk would have been protected from UV damage, although oxygen in the atmosphere could affect paint color after 50 years also? The ash try (on the right in the photo) is the paint mixed locally without having had a physical reference to match.
Thread:
Not a Match (Paint)

trunk latch.JPG