When they have CCTV in the bays yes its going to matter rather a lot as the OCR software will be looking for your number plate and potentially if its clever enough check the colour and maybe even what car it is (not hard for it to learn what a sierra looks like etc if they go that far with it) and of course if you do get a person glance at it then its really an issue if there isnt a car of the right type and colour with the correct reg plate sat in the bay!