Wow, that is great news !! I have been hunting for the very same thing...the interior color of the cab for my Mariner Blue Chevy 6400 truck.
The old PPG 31104.
I really appreciate all your research and info here.
I too was having trouble finding the old PPG formula, and it sure makes sense now, what you state.
Will get with my local PPG person to check this out further, thanks again Denny, and all you Chevy people !
:p
MJD