I restore pinballs and can tell you that when you touch up something that old, there is no color code that will get you a match. Colors fade, and the fade becomes the color.
For the vent covers just take them off and repaint entirely.
For spot repairs to the body, you will never 100% match a color such that it won't show. The oxidation in the paint
you didn't touch up will have a different sheen, which will show as a different color in most if not all light
Pinball guys usually paint
the whole side or leave it. Spot touch ups always look like spot touchups. If they are touching up bare wood sometimes a spot touch is better but still looks like a touch up.
As far as color matches, I have gotten very good at this over the years, but can you tell me what kind of paint
you'll be using so I can give proper advice?
Here is example when I say restore pinball.
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