Roman Centurion cloak and plume

[Purplest]

Early centurion helmets, like the Coolus helmets, used a central horse hair tail mounted to a spike on the top of the helmet and had feathers mounted on the sides in plume tubes. Later centurion imperial gallic helmets had a horse hair transverse crest or a feather transverse crest. As far as color, there appears to have been a number of different colors used, such as white, black, red, yellow, purple... A lot of what is known about crests in general is from writings and sculpture as no complete crest (to my knowledge) has been found. Hope this helps.
As far as the color of cloaks those varied as well.. Just like the color of tunics and subarmalis. There wasn't just one particular color for these items.

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