Also red was an expensive colour...obviously like in the British Army of the 1600 to 1900 there was an cheap version of dye and an expensive one for the high class. I presume the wealthy soldiers could afford a red tunic , for the others white, natural or other colors sufficed. The ideal as painted on walls in Pompeii was red..but i think everyone had a tunic of a colour different from the other...not white, mainly natural color of wool or linen. If i was FL i'd choose to do a third version off-white representing the colour of the fabric not dyed.