I'm doing a Republican Roman force for Clash and I'm going for a range of red/browns - terracotta, madder, etc, plus some off whites and minimal pale blue. Although there's no evidence for its my triarii will have bordered tunics too.
I'm doing a mix of shield designs/colours per unit and weaponry will indicate which units are which. I'm actually doing a mid/late 4th century BC army to fight The Gauls and Samnites so my hastati will have javelins/pila, my principles short spears and my triarii longer spears plus hoplite shields. My triarii will also have full bronze breastplates while the principles and hastati tend to have more of the small chest plates. No mail in my 4th century force, although I am planning to paint additional models for a mid 3rd century force so some triarii in mail and hastati and principles all armed with pila and swords.
Regarding weaponry, this is all based on stuff I've read recently about weaponry/tactics in the 4th century BC in Italy, although they'll all function as per whatever the rules say for Punic War Romans...