Same thing happened me, except i bought the car off the floor put down deposit and then it turned out to have been already sold by the corporate section and they hadnt updated the car or the system. I was offered a different colour but stood my ground, and ended up getting the exact spec of car i wanted shipped in from Port Macquarie.

Id be getting them to try and source one from another dealer as they all should have visibility but dont always use it as it costs them to transport cars around.

The other thing i guess and this is just from my perspective is that maybe they are trying to save you the pain of owning a black car, i swore never again....