Keep in mind that the colors you're seeing on-screen and in photographs will not generally be accurate out in the real world. Your color picker will work fine if you want something close for a signature or email header or the odd word document. I would not use that for a reference to actually buy paint with.
Unless your monitor is color calibrated, and the photographer was meticulous in post-production, and you're both using the same standard--which is probably not the case--you're better off color matching with an FS number or equivalent. Most automotive paint brands already have accurate matches anyway.
Trouble with car stuff is there are just too many darn experts, huh? Try this on for size:
Filling Station Chevy Gray 
