One of my all time favorite roman fiction author, Steven Saylor, made a harsh comment on the color scheme used on the Roman sets in Gladiator.

"When will we see a Rome that looks as Rome really looked — more like riotously colorful Mexico than monochromatic Washington D.C.? Just as the Mexicans wash their plaster walls with color and paint their wooden or plaster statues of saints, so the Romans loved color in their homes and painted their statues of gods and heroes to look as lifelike as possible— but Hollywood has never learned this, so once again we see a Rome drained of all color. The interiors of the palace are as sterile and depressing as a bank vault. Anyone who’s ever been to Pompeii knows the charm of the human scale of Roman homes, even the largest (such as Hadrian’s villa)"

Although his criticism of the film may be exaggerated in some points, I couldn't agree more with him and this matter. Hollywood ,as the pre Raphaelite painters before them (which, by the way, I love, despite their faults), have always strived to show their viewers a kind of aseptic Rome, glittering with shiny white marble.
A vision of the Rome that could more accurately placed in Thomas Moore's Utopia, than in the cold, hard evidences archeology has brought to light.
Gladiator showed us for the first time a dirty, decadent (although still beautiful Rome). But it exaggerated on the decadence part! I was shocked to see the decoration of senator Graccus's palace, in the extra section of the Gladiator Dvd. The walls ware bare stone, except from the decayed painted plaster remains, scattered about it.

If you want to read the whole review, go to this page

http://www.stevensaylor.com/Hwood_Texas.html

Be warned: it's very corrosive:-))