When paint is not exposed to UV light it fades at a different rate. The color under could be a result of the paint not being exposed or it could be the adhesive from the decal. It might be the decal itself getting old and failing but leaving the film behind. Either way, from what I can see in the photos the paint looks to be original IMO.
Wish there was at least one photo of the engine, trunk and underside. I would like to own that car, but not enough photos to tell really what you're buying.
Seller advertise the car as a original paint car but how come there are darker orange under the ripped stripes, and paint in the door screws?