How did legionnaires from each opposing side distinguish friend from foe? Did they wear different or armor or did their armor have different colour or something in those bouts?
It should be noted that the picture of the battle descending into a chaotic melee with combatants of both sides intermixed is a Hollywood thing, and not something that'd happen in real life for various reasons. More can always be said on the matter of pre-modern combatant identification, of course, so if anyone would like to have a go at how the Romans did this bit, don't let this post stop you! For the meantime, OP, combat identification is rather one of the more frequently asked questions for you, so in case you don't get anything new, here's some previous posts: