The place that he got the spray paint from used the color code to match the paint color... Just tell them your factory paint code and they will make you as many cans of paint as you need...
That only works if it is a recent paint job and they actually got it right. I watched a guy buying paint at my local paint store. He brought a piece of the car and they fanned out a deck of maybe a dozen shades of that color to match the fade.