Making a Sprite Smaller after Colliding to an Object

I can’t figure out how to make the black overlay’s scale smaller each time it hits an object, Voidon. Here’s a link to my scene.

I’m not sure about this code, but is this correct? And, how do I implement this?

entity.setLocalScale(0.9, 0.9, 0.9);

The part of the code with collision.

HeroMovement.prototype.onCollisionStart = function(assets) {
    if(assets.other.name == "gas"){            //assets - other assets in the map
       assets.other.destroy();
    }

    if(assets.other.name == "Voidon"){            
       assets.other.destroy();
    }

};