My next is a OO like yours. As I said, I've never had a problem getting paint and obviously neither has Jerry or others. Some places don't like non-accounts. You seem partial to PPG. I've shot PPG and others as well.
I need OO paint so I called the PPG library today and was given an offset as it is not available mixed with the tints in the system. If you've ever mixed on a system this would be clear. My MM is a direct mix -- OO is not. It's offset is PPG 61039. It is lighter than prime. May not even be enough to tell. Once again, if you ever look at variances on a system, new cars can have up to 3, 5 or more.
You can have it mixed in DBU or DBC (the latter my preference but more $). DBC can do something helpful other paints cannot.
Your other choice is to shoot a lacquer panel . Then shoot a 61039 panel and see what the difference is. No matter what they are chemically different and will lay down differently. But still, the tints are not the same anyway, this is why an offset is given. So now it's up to the man using the tints to darken the prime color first mixed. Keep in mind the lacquer was never cleared from the factory. And I'm not going to get into the principles of reflection and refraction. They will make the colors look different as well. The PPG libtrary phone # is 1-800-647-6050