Glad you're in the road to success, John.
Somewhat related... About 45 years ago I was focused on HO trains, but didn't have a layout as yet. Athearn offered a series of their 'blue box' kits for Santa Fe reefers in different slogans. I bought several of them, built them, and put them in a row into a display cabinet on a wall in a spare bedroom. The display cased was on the opposite wall of a south-facing window. Items in the display never saw direct sunlight, but particularly in winter months the room was very bright.
Well, about 25 years later we moved. As I removed the reefers from the display for packing I was amazed at the difference in the orange color on the two sides of each car! The sides facing the window were mostly yellow with a hint of orange, those facing the back of the cabinet were orange with a hint of yellow!! To see how faded the one side had become, I lined up the cars alternating their original orientation. Holy moly!....what a difference!
So, if the paint doesn't have UV stabilizers...and most hobby paint doesn't...or a UV stabilized clearcoat, who knows what the original color would be?....and what difference does it make for contemporary matching anyway?
KD (Lucas Gudinov)