The last people to live in my house decided to use black spray paint on the bathroom tiles and it looks awful (not to mention the fact that it is peeling and uneven as it wasn‘t done properly). However the tiles underneath are blue and white so I would like to keep them. What is the best way to remove the black paint without scratching the surface of the ceramic tiles?
Try baby wipes. They are surprisingly effective on tiles.
You can try paint thinner and a heavy scrub brush, it worked for me, or you can get some professional tile cleaner.
The best way to remove paint without ruining the tiles with scrape marks is to use a chemical stripper. Try a spot in an inconspicuous place. My only concern for you is that the grout might have absorbed the black paint so the black tinting may remain once the paint is removed from the tile. Your test spot will reveal the results and you can decide to follow through with the rest of the room or not. Sometimes you have to wonder what the hell goes through the minds of people when they decide to do home improvements. I