Add a post process component to the player class. Adjust the PP to have the effect you want. Set the PP disabled by default.
Create an Actor class. Name it Play Zone. Add a Collision component…say box.
Box collision settings: ignore all, overlap Pawn.
End overlap: Enable character post process.
Begin overlap: Disable Post process.
Add the Play zone to the level. Scale it as needed.
When the player leaves the play zone the PP will be enabled and apply the base effect. You can add an event that triggers a per tick trace to get the distance from zone and adjust the PP settings as needed.
When the player re-enters the zone (begin overlap) the effect is disabled.