Guards were members of various military forces throughout Italy; and were used to defend and control locations or certain individuals. The colors and styles of their uniform varied to denote rank, allegiance and combat specialization.
Some of them (like the Militia) were underpaid, had low morale and would flee from battle if they were losing. Another example would be the Agile, who would climb up to the rooftops if they were pursuing Assassins. Depending on the armor they were wearing, some guards were able to withstand more damage and were better at dodging enemy attacks.
Leaders and Captains were equipped with more advanced pieces of weaponry and armor.