How much of the statues were painted - all of it, including clothing?
All of them — same way that those lawn gnomes are painted today. :’)
The Elgin Marbles, which were removed from the Parthenon early in the 19th c, wound up at the British Museum. Some touch-holes there didn’t like the remains of the original paint job (from the 5th c BC), and over the decades various methods (scraping, sanding, acid) have been used to remove the paint and the accumulated weathering.