It’s a common myth that classical marble statues were pure white and boring. In fact it’s modern consensus that they were very often skilfully painted, but the colours were lost to time.
Augustus looking very fine there.
Source (in Spanish): http://rodrigorivas3d.blogspot.com/2014/05/policromia-en-la-antiguedad.html
For the sculpting portion: the finest craftsmanship you can muster, artisans! Make it as if the man is truly right in front of you and that to touch that statue would be to touch soft skin and fabric!
For the painters: just slop it on
There must have been a sculpture that had the biggest delta between the quality of crafting and the quality of painting. The funniest work of art
An Ancient Roman version of this where someone with a pallet of 5 colors tried to spruce up a beautifully detailed statue