The red car is known to be have been stripped and returned to its original stainless, by an owner unaware of its history. The black car is now known to be in private hands in New Jersey, but has been re-painted in blue. The whereabouts of the yellow car are currently unknown.
Many painted DeLoreans exist today in various colors - some were painted by the selling dealers when new (giving rise to the stories of factory painted cars) and still others were painted by their owners. Nevertheless, that doesn’t change the fact that to most DeLorean enthusiasts and prospective owners, a painted car will always be worth less than an original stainless steel example. Generally speaking, for two DeLoreans in identical mechanical and cosmetic condition, the painted car with be worth approximately half the value of the stainless one.
There are stories, some true, of DeLorean cars that were damaged (in accidents or otherwise) and subsequently painted to hide the improperly repaired damage. If considering the purchase of a painted car, it may be wise to have it examined by a paint/body shop, who may be able to point out areas of repair beneath the painted surface.
It is possible to take a painted DeLorean and return it to its original stainless finish. The process can be expensive and time consuming, depending on the condition of the body panels under the paint (dents and dings that have been repaired with filler, as well as how the surface of the panels may have been sanded in preparation of painting). Once the paint has been removed, and any body damage repaired, the grained finish must be restored as well. Replacement or repainting of the urethane bumper covers must also be considered.
Unless you have the skill set to complete most of these tasks yourself, if you want a stainless steel finish on your DeLorean, it is usually more cost-effective to buy a stainless car. Conversely, for the expense (and decrease in value) involved in painting a DeLorean that has never been painted before, it is usually more economical to buy an already painted DeLorean.
Updated September 5, 2016 - location of black car