ViewController.swift

  override func viewDidLoad() {
    ...
    statusListener()                                                  //(1)
  }

  func statusListener(){
    Firestore.firestore().collection("settings").document("device1")  //(2)
      .addSnapshotListener { documentSnapshot, error in
        guard let document = documentSnapshot else {                  //(3)
          print("Error fetching document: \(error!)")
          return
        }
        guard let data = document.data() else {                       //(4)
          print("Document data was empty.")
          return
        }
        let status = data["status"] as! Int
        let color = UIColor(hex: data["color"] as! String)            //(5)
        self.setStatus(status: status, color: color)                  //(6)
    }
  }

  func setStatus(status: Int, color: UIColor){                        //(7)
    let LABELS = ["Started","Going","Stopped"]
    selectionSegment.selectedSegmentIndex = status
    statusLabel.textColor = color
    statusLabel.text = LABELS[status] 
  }