I think that I get the question.
A few years ago I had a slight bump on the front wing of my TR and it was repainted in what was an 'identical colour' matched paint. The problem is that over time they have aged differently and the wing is now a completely different shade than the rest of the car.
Maybe if the repaint was not only the same colour, but also the same brand, they would both have aged gracefully together.
Is that what lies behind the question?
That was how I read the question from the OP - the same fade rate being important.
Exactly!
