I would go along to a proper automotive paint place with the hard top on and get them to match the colour to the car and say you want it as a spray paint (in your case an airbrush). This is what I did with my, ahem, knob, which needed the silver 'alu look' paint redoing... they used the actual part I left with them to make the paint up. I was astonished by how close a match they got.
They asked if I wanted it as touch up or spray, and explained the consistency is different.
They asked if I wanted it as touch up or spray, and explained the consistency is different.