How to use the angular-cesium.PickOptions.PICK_FIRST function in angular-cesium

ngOnInit() {
    this.cameraService.cameraFlyTo({destination: GameMapComponent.DEFAULT_START_LOCATION});
    this.mapEventManager
      .register({event: CesiumEvent.LEFT_CLICK, pick: PickOptions.PICK_FIRST})
      .subscribe((result) => {
        const clickPosition = this.geoConverter.screenToCartesian3(result.movement.endPosition);
        const existingPoint: PathNode = result.entities && result.entities.length && result.entities[0];

        if (!existingPoint) {
          this.createNewPathNode(clickPosition)
        } else {
          // update existing point
          this.updatePathNode(existingPoint);
        }

        this.polyLinePoints.push(clickPosition);
      })
  }

ngOnInit() {
    const mouseOverObservable = this.mapEventsManager.register({
      entityType: Track,
      event: CesiumEvent.MOUSE_MOVE,
      pick: PickOptions.PICK_FIRST,
      priority: 2,
    });

    // Change color on hover
    mouseOverObservable.subscribe((event) => {
      const track = event.entities !== null ? event.entities[0] : null;
      if (this.lastPickTrack && (!track || track.id !== this.lastPickTrack.id)) {
        this.lastPickTrack.picked = false;
        this.layer.update(this.lastPickTrack, this.lastPickTrack.id);
      }
      if (track && (!this.lastPickTrack || track.id !== this.lastPickTrack.id)) {
        track.picked = true;
        this.layer.update(track, track.id);
      }
      this.lastPickTrack = track;
    });

ngOnInit() {
    this.tracks$ = this.dataProvider.getDataSteam$().pipe(map(entity => ({
      id: entity.id,
      actionType: ActionType.ADD_UPDATE,
      entity: entity,
    })));

    const mouseOverObservable = this.mapEventsManager.register({
      event: CesiumEvent.MOUSE_MOVE,
      pick: PickOptions.PICK_FIRST,
      priority: 2,
    });

    // Change color on hover
    mouseOverObservable.subscribe((event) => {
      const track = event.entities !== null ? event.entities[0] : null;
      if (this.lastPickTrack && (!track || track.id !== this.lastPickTrack.id)) {
        this.lastPickTrack.picked = false;
        this.layer.update(this.lastPickTrack, this.lastPickTrack.id);
      }
      if (track && (!this.lastPickTrack || track.id !== this.lastPickTrack.id)) {
        track.picked = true;
        this.layer.update(track, track.id);
      }
      this.lastPickTrack = track;
    });

this.lastPickTrack.picked = false;
        this.layer.update(this.lastPickTrack, this.lastPickTrack.id);
      }
      if (track && (!this.lastPickTrack || track.id !== this.lastPickTrack.id)) {
        track.picked = true;
        this.layer.update(track, track.id);
      }
      this.lastPickTrack = track;
    });


    // Open dialog on double click
    const doubleClickObservable = this.mapEventsManager.register({
      entityType: Track,
      event: CesiumEvent.LEFT_DOUBLE_CLICK,
      pick: PickOptions.PICK_FIRST,
      priority: 2,
    });
    doubleClickObservable.subscribe((event) => {
      const track = event.entities !== null ? event.entities[0] : null;
      if (track) {
        this.ngZone.run(() => this.openDialog(track, event.cesiumEntities[0]));
      }
    });
  }

ngOnInit() {
    this.eventManager.register({
      event: CesiumEvent.LEFT_CLICK,
      pick: PickOptions.PICK_FIRST
    }).pipe(
      map((result) => result.cesiumEntities),
      filter(result => result !== null && result !== undefined), )
      .subscribe((result) => {
        console.log(result[0]);
        alert(result[0].ellipse.material.color._value);
      });
  }

testColorChange() {
    const inputConf = {event: CesiumEvent.LEFT_CLICK, pick: PickOptions.PICK_FIRST, entityType: AcEntity};
    this.eventManager
      .register(inputConf)
      .pipe(
        map(result => result.entities[0]),
        filter(entity => entity.id === '0'),
      )
      .subscribe(entity => {
        console.log('click3', 'toggle color');
        entity.color = entity.color === Cesium.Color.GREEN ? Cesium.Color.BLUE : Cesium.Color.GREEN;
        this.layer.update(entity, entity.id);
      });
  }
}