Just added another section to the Suspension Guide I have been working on in my spare time. The full version is on my website - this link here is for just the section on all the different original pitman arms used from 1965 to 1973. I added notes on correct paint dab colors where I am sure, but others I left blank as I have conflicting data so if someone has information with known original examples let me know and can update.
Nice job
I've found different paint markings on some parts between originals and service parts this may explain some of the conflicting findings you mention
Example would be "1965/66 eight cylinder Mustang C5ZZ-3590-A".
Have originals (65 in this case that I'm looking at) marked with a white and muddy red/red oxide. While have pictures of service parts marked muddy red/red oxide and light blue
Paint markings may only apply to certain production periods since things can change and processes refined
1965 and 1966 Shelby GT350 only, S1MS-3590-A - Often found with yellow paint on later 66 built units