Resistance is indicated in the Noise Report, and can range from 0% to 200%.
If the resistance rate is 200%, then the Noise will absorb the attack's damage. This is indicated by green numbers showing health gain rather than health loss.
If the resistance is less than 100%, then damage from that psych element will be super effective and deal greater damage than what it would deal if the same Noise had a higher resistance. In this case the damage will be indicated by yellow numbers preceded by the symbol for positive or negative psychs.
If the resistance is more than 100% but less than 200%, then the damage will be reduced. This is indicated by ordinary white numbers preceded by the symbol of either negative or positive psychs.
If the resistance is exactly 100%, then the Noise has no resistance or weakness to the element, and damage output is relatively normal. This is indicated by the normal white damage numbers preceded by no symbol.