Auras in C9 play a very big role, they decide wheter an attack will hit/stun the opponent or not.
Invincible Frames also known as "iframes" make your character invicible saying that when an attack hits you, your character will not be interrupted nor stunned nor taking damage. They show up as a white aura.
Super Armor is shown on the character as a red aura. Basically its an aura that makes you much more endurable to most skills in the game. You can't get stunned, other players will be able to grab/throw you though.Some certain skills can break super armor.
Semi-Super Armor (blue aura), does the same thing as Super armor, only that it is much more rare and is easier to break than Super Armor.