Engine paint decision and questions

In regard to the International Harvester red paint I have seen that for some reason it is now a darker red. My Dad used to restore IH tractors and his garage has partial cans of IHC red paint from the early 70s to 2009. I got a quart of IHC red from Tractor Supply about a year ago to paint a friends engine and it looked really dark to me. I got a few cans of the old stuff from my Dad's garage and poured them together to have enough paint to get the engine painted. Then out of curiosity I bought five spray cans of IHC red from different sources and each of them is a good bit darker than my Dads old paint. I even sprayed them on a hitch bar of a tractor he had painted several years ago and the new paint is not a match, being much darker than the tractor.