Fun fact! Those statues were actually painted in garish bright primary colours, it's just that the paint was expected to last a few decades at most, and when these statues were found in the renaissance, the paint had chipped away long ago, just leaving the plain marble behind.
Some were probably garish, and we can probably safely assume the ones that were out in the open were painted sort of like the statues one might see at a mid 20th century tourist trap due to the limitations of Roman paints and the need to regularly repaint them, but ones set under cover in a villa courtyard (but still outside: the better/longer lasting Roman paints apparently fucking reeked to the point that they weren't suitable for indoor paintings, hence the dominance of mosaics for decoration inside) may well have given 20th century wax statues a run for their money in terms of being eerily lifelike.
Something that's important to remember about the paint traces is that anything stuck to the statue itself would be from a basecoat, and when painting onto something like a statue or figure you need undercoats of bolder colors to help the higher coats look right. So it's likely that some portion of protected statues would have been painted to the same standard as the finer paintings that survive from that era (almost all of which are funerary paintings from Roman Egypt which were sealed away in an extremely dry and stable climate - it's likely paintings of the same quality existed everywhere, but didn't survive beyond the most fragmentary pieces).
Fun fact! Those statues were actually painted in garish bright primary colours, it's just that the paint was expected to last a few decades at most, and when these statues were found in the renaissance, the paint had chipped away long ago, just leaving the plain marble behind.
Some were probably garish, and we can probably safely assume the ones that were out in the open were painted sort of like the statues one might see at a mid 20th century tourist trap due to the limitations of Roman paints and the need to regularly repaint them, but ones set under cover in a villa courtyard (but still outside: the better/longer lasting Roman paints apparently fucking reeked to the point that they weren't suitable for indoor paintings, hence the dominance of mosaics for decoration inside) may well have given 20th century wax statues a run for their money in terms of being eerily lifelike.
Something that's important to remember about the paint traces is that anything stuck to the statue itself would be from a basecoat, and when painting onto something like a statue or figure you need undercoats of bolder colors to help the higher coats look right. So it's likely that some portion of protected statues would have been painted to the same standard as the finer paintings that survive from that era (almost all of which are funerary paintings from Roman Egypt which were sealed away in an extremely dry and stable climate - it's likely paintings of the same quality existed everywhere, but didn't survive beyond the most fragmentary pieces).
Oh, I didn't even think about base coats. You're right, it probably was brighter and more intense so the other coats could add detail.