The new Korvara dungeons don't really benefit much from the current Iahsus colors, the only one that generally applies is orange Iahsus due to it boosting the miniboss spawn rate, here are my suggestions to make them closer to the Sigrogana counterparts:
Purple Iahsus: Monsters spawn a little bit weaker than before, always appearing 5 levels lower than normal (Minimum level is 1 still)
Yellow Iahsus: Monsters have increased patrol rates and are more likely to aggro onto you from farther away.
Red Iahsus: Monsters spawn a little bit stronger than before, always appearing 5 levels higher than normal.
Purple Iahsus: Monsters spawn a little bit weaker than before, always appearing 5 levels lower than normal (Minimum level is 1 still)
Yellow Iahsus: Monsters have increased patrol rates and are more likely to aggro onto you from farther away.
Red Iahsus: Monsters spawn a little bit stronger than before, always appearing 5 levels higher than normal.