It's not that it's that hard to match. In my case, it was that my dealer just switched to a new paint vendor (to Sherwin Williams from DuPont). They took two weeks, and painted it three times, with the paint engineer flying in from Sherwin Williams to advise until it was right. Now that they have it figured out, I'm certain that it will be perfect next time (when I get a V rear bumper).
It cost me a bundle (they kept to their estimate, even though it took them much longer to fix), but it was done right. Mine now looks perfect and is indistinguisable from the other factory painted panels. I also got a lifetime color match guarantee.
Get a spare grill and have them paint it until it matches. It's their problem to fix, if it's not right, even if you go to Maaco. Do the install yourself.
I've been told the toughest color to match is the white pearl.