Mike,

I just end up custom-blending hobby-paints for small touch-up areas.  With practice I have gotten pretty good at doing this and it is very hard to see the small touch-ups I have done on some of my machines

For larger area, I might just do a repaint with spray-paint on an entire section.

Some folks will take a cover off of a machine down to their local paint store and have them computer-scan it and make up a small pint or quart of custom-mixed paint.

Factory original paint is exposed to sunlight, UV light, and such that will change the appearance of a factory colour over time.  I have some machines that even have differing hues of the same colour...result from the machine sitting near a window and getting sun-fade on only some exposures of the machine.
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