There was a factory stamp in yellow paint that went in that location on the RV-2 a/c compressor. If you want to see all of the possible paint colors, stamps, etc., check out the restoration parts area of the Mopar hobby. They can be purchased new for letter-perfect A/B/E body restorations, but many cross with C-body cars too.
All of the stamps, daubs, and grease pencil marks indicated an inspector checked that item for correct installation/bolt torque. All of that has been documented over the years in various Mopar-oriented magazines, but the main thrust is in the B/E-body cars, where HEMIs resided and multiple $$$$$$ can result . . . for correct cars.
CBODY67