Remember when LCT made their last run of the standard gauge Blue Comet?...and the passenger cars arrived with some serious paint chipping along the top edges of the car sides where the roof contacts? I believe MTH stepped up for the few that insisted they do so...but never heard how that all turned out.
Mine wasn't so bad as to go through the hassle of re-shipping, waiting, wondering, and ...being unhappy a second time?????
So I took a car to the local Pittsburgh Paint outlet. When I was trying to match a particular stain on a cabinet project, they hit a pint's worth of mix spot on!...in less than a day! The guy took a look at the car, said to come back in a couple hours. (I was working at the LHS across the road at the time).
When I went back he had prepared a pint of blue brew that, though not quite spot on, was 'good enough' (until paint dries...thoroughly...you never really know what the final color will be...IMHO. (By then I had been given the alias 'Lucas Gudinov' by the LHS crew for my soft standards in modeling and finishing!)
Big Box places...like HD...have a DIY color-analyzer-matcher gizmo that will come pretty close on home improvement items. But you'll need to buy a quart or gallon of paint for them to create a sample. Even then, how fussy are you?
Automotive paint stores?... Never tried, but I expect the bigger, well-established, reputable ones would be best capable of matching colors.
Color matching...to either something existing, like of a paint brand that's no longer made!... or your senile, cataract-troubled memory of yore, about as accurate as recalling the date of your wife's birthday or your anniversary!...is one of those never ending model railroading conundrums. You know, the hobby's PTSD...Paint Traumatic Stress Disorder!