Friend or foe? Just colors?

[TITVS SABATINVS AQVILIVS]

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In the civil wars battles among legionaries, how they could recognize friends or foes? ?<br>
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During an intense (and dusty?) fight, stated the difficulty of recognizing the different units by means of standards and sounds, how each soldier could avoid to kill his own "commilitones" for mistake?<br>
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I guess that having the same tipe of equipment, the different fighting legions could be recognizable by means of different colors of: tunics? Shields? Crests? Plumes? Or what?<br>
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Any evidence about temporary colors water paints?<br>
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Ualete<br>
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Titus Sabatinus Aquilius <p></p><i></i>