A few years back I worked for Halliwell Jones and matching repairs to existing paintwork in any light coloured metallic was a nightmare ! The robots that paint the car at the factory are programmed to spray the absolute minimum amount of coloured basecoat over the primer....annually this saves them an awful lot of money ! Unfortunately this creates the problem of the primer showing through or 'grinning through' this very thin layer of colour coat. This alters the actual shade of colour basecoat. If you then imagine a guy in a bodyshop spraying his own primer (different shade ?) by hand followed by light metallic colour coat and lacquer. He is probably spraying all layers several microns thicker and possibly not as evenly as the factory. No wonder it's hard to get a match !
Your average man in the street would probably never notice it but it would annoy the hell out of me, as it obviously is you too ! :x

Your average man in the street would probably never notice it but it would annoy the hell out of me, as it obviously is you too ! :x