I've noticed these "tiger stripes" on a lot of silver coloured falcons. I don't think its normal or acceptable. I have Mercury silver as Kappie does, and i have checked it in a quite a few different light conditions. No tiger stripes, so i don't think you should accept it Kappie. There is however a small colour variation in the rear bumper, I can just notice it in full sunlight.
I made sure when i picked up the car that the paint was ok.
Kappie i would talk to ford about the tiger stripe situation.
5 speed or Nothin' Mercury BA Falcon XR6 Manual with 18's, Whiteline Lowered Springs, Adjustable Sway Bars, and Herrod Exhaust......mmmmmh