I seriously wouldn't be surprised if that person spray painted their seats, but that is a really stupid way to change the color of you upholstery. Why ruin the interior of a relativly new car by spray painting the leather?
The correct way to change the color of your seats is to re-upholster them with new covers. I got my Katskin upholstery from this place... http://www.autoleathers.com/HTML2/AL.MAIN.FS.html
IMO, this guys interior turned out really bad. Look at the scratches he already has under the air bag, and look at the paint chipping off the door sill. Plus, the texture looks like he really caked the paint on, looks really bad to me.
To do a color change on the interior plastics, you need to remove the plastic parts, sand them a bit to help the paint adhesion, then just paint them. I would reccomend using a dye instead of a conventional paint. You spray the dye just like regular spray paint, the main difference between the dye and regular spary paint is that the dye is thinner and more durable. Due to the fact that the dye is thinner, it is able to seep into the small pours in the plastic which will result in better adhesion.
I would reccomend doing a search on interior color changes. This has been discussed a few other times, so you should be able to get some good tips from the other threads.