If the car has original Ford paint, you can get a Model A Ford Paint and Finish Guide at most model A suppliers for about $30 or $35. It has all the color chips in it and the years the colors were used. Typically there were only 4 or 5 colors used for each year, so it usually isn't difficult to figure out which of the colors it is. If you aren't 100% sure you can take the booklet out to the car and compare the booklet to the car. I have the Dupont and PPG color mixing codes if you can't find them for the color you pick. Also, it is a good idea to have the smallest amount of paint mixed (usually 1/2 pt) and test spray some of it to make sure it is what you want. I have had two PPG colors (Copra Drab and Bonnie Gray) that were the wrong color.
Rusty Nelson