Here is a photo for some colours I have used to liven up my Romans. Hope its of some help... red spears, green red scorpions, linen/wool tunics for some
As an alternative to the more traditional red I've gone with blue for mine. The reason for that stems to the old Rome Total War PC game where my preferred Roman start up were the Scipii who were coloured accordingly to differentiate from the other two Roman factions. I have seen since though that there's a school of thought that there were some blue tunics often associated with their marine type regiments as well as some auxiliary troops. I have read of some suggestions of greens and oranges but over all there's some dispute over most alternatives to red.