I think this will help, although my Mach 1 is a 70 and not 69, it was a very early Dearborn built 428 CJ with C6 and came from the factory with a 69 tube and dipstick on the tranny along with several other 69 parts in various locations. I have owned this car for over 30 years and the original paint on the tube is still in excellent condition. I am also in the process of restoration and took my original dipstick into the paint shop today and had it camera scanned and a paint chip selected from that scan which was used to compare against the tube. I then had them custom mix me a rattle can of the paint and I sprayed out a test card and I believe it is pretty close, maybe very slightly brighter, but then the tube is 50 years old so you would expect it to have faded a bit, but I am guessing not much as I have had the car in heated storage all the time I have owned it.
I document all my restoration work for future reference and have placed the original untouched tube over the test card for comparison and the paint formula is on the page for your reference. The paint is a Valspar acrylic enamel. You will have to find a shop that can custom mix this acrylic enamel and you should be all set. The rattle can costs about $25 to get made up.
