A lot of the reasons old structures and sculptures were painted was to highlight wealth. Most building materials were common wherever you used them, so you coul

A lot of the reasons old structures and sculptures were painted was to highlight wealth. Most building materials were common wherever you used them, so you could imagine the marble mine used that led to the statue was probably not more than several hundred miles away. The paint, however, may be very exotic. Certain colors and tones were infamous in the old world for being extremely expensive, be they hard to make or find, and often had to travel thousands of miles. When you painted your stuff, it was to show off that you were not only locally rich, but you had the connections internationally to get the really care stuff. Not sure if that was the case with the Augustus statue in question, but it is common throughout Greek and Roman architecture.