Phasma’s armor is made of shining chromium, and was made from parts of Naboo yacht of the Empire leader, Palpatine. Phasma also wore a black cape with red fastening, which was, with the unusual material of her armor, her symbol of power and dominance. She has been clearly seen in battle, leading her troops, which had also motivational aspect.
Her armor had a lot of connection to old empire. Being made from imperial yacht, was a sign of lost old glory, which can be restored by First Order’s pursuits. That was probably appeasing Phasma’s ego, as she was as much a symbol herself, wearing it in front of her soldiers.
Her armor was very durable, and could stand a lot of pressure and it would be really hard to harm her. It had also ability to bounce back gunshots, so she was more protected than other troops.
She led her people to victory, the heat of the battle reflecting in chromium wildly, her expressionless helmet showing no emotions, thus no fear… she really was making impression of being unbeatable.
Bless you, Phasma’s armor.