Yes, the MRH guide (link below) is a great start. I am hoping to add to it as it has limited specifics that so many on this list might want to know. For example PRR FCC would be important for many freight car modelers in our era.
I will contact you off list to see if you would be willing to supply some 2"x2" paint sample of your colors and I will reciprocate. My thought is exchange 2"x2" samples on white styrene so we don't have to buy every color. Then as we develop formulas that match existing favorite colors we can share them broadly.