I saw such a thing in such a place less than 10 years ago. They matched some paint for a job I had in and it wasn’t bad.
A significant issue can be the glossiness. For cars the default is high gloss, but they can add varying amounts of matting agent to take that down. We had to guess when they did my can. Again they were quite close.
I’ve seen a lot of Quad IIs and Stu’s right - environmental factors (sunlight, heat, fag tar, corrosion, pet wee etc) make a big difference over the years. All the Quad IIs you ever see now are matt grey, assuming they haven’t been resprayed, but in this pic
you can see the EF86s reflected in the output transformer (I think the lighting would have to be very unidirectional for those just to be shadows). So once upon a time … they were all shiny !