1stcentury off-duty clothing

[Caius Fabius]

off duty? I wonder if the Roman army centurion was ever really off duty, and could have distinctive dress for those times? Or is this a modern concept? Perhaps the Roman centurion was always wearing a red tunic, even when 'off duty', and carryng a vine staff? Maybe the reason the centurions petitioned to wear white during one triumph, was so they could join in the after parade festivities without having to be 'on duty'?
We always seem to see the past in the framework of our modern day experiences.