Photoshop question
I would begin by drawing a selection with the pen tool around the car.
Feather the selection by 1.
Copy the car - Ctrl-C
Image > Mode > Grayscale (make everything B&W)
Image > Mode > RGB (Turn it back to color (image stays B&W))
Paste the copy of the car (Ctrl-V) in the same x,y location as in B&W layer.
Merge the layers, done.


That be the easiest way.