The Greeks and Romans both painted their marble (etc.) statuary. It's just that the paint has faded and worn off over the millennia since, leaving modern audiences to consider their white marble and other stone to be a "classic" look, whereas the ancients would have considered that as unfinished and odd as we consider office buildings wreathed in colorful insulation panels before being covered over and painted a nicely neutral tone.
Ultraviolet light reveals how ancient Greek statues really looked
Original Greek statues were brightly painted, but after thousands of years, those paints have worn away. Find out how shining a light on the statues can be all that’s required to see them as they were thousands of years ago.
Wow! They did like their loud colors, didn't they? I guess it makes sense. Since a lot of statues were built to honor various gods, I guess bright colors were used to make sure the gods noticed the work? Or maybe they just really liked bright colors.
Color is eyecatching and interesting, as well as a sign of wealth. The wall paintings in Pompeii show that, in lieu of colorful tchotchkes and hung artwork, paint was used to decorate. It's not at all surprising that exterior paint was used as well; it only seems odd because that's not our modern tradition, and in part that's because we've been so influenced by the time-stripped paintless buildings of the ancients.