Battery And Battery Cables

Of course the old die hard battery was 5 years old and was dead.
The scary part to me was that as I was taking the battery out the red cable was on the negative post of the battery?
I heard these older vehicles might be positive ground but I then read up and one person online said they had removed there battery and the same!
So I did some research and in 1960 it should have been a negative ground. I guess at the factory they had red cables leftover from when they were positive ground that they were still getting rid of or someone just had that laying around and put it on in the past.
I put the new battery in just I painted the red cable from the factory black and the black cable to the starter from the factory red.
Hopefully this will all work when go to turn over the FC for the first time?