Technically, he is correct.
This is a great example of why taking things literally is not always the right thing to do. Sure, this person's car is indeed green. But did they really think that's the kind of green intended on the sign? What would be the purpose of an all-green colored parking lot?
Why would owners of green-colored cars be favored over everyone else? But maybe this person is actually smarter than we're giving them credit for and parked there as a joke, purposefully misreading the intention of the sign.
