Swift 2 - 从另一个UIViewControl更改UIView背景颜色

Question

我想在集合视图控制器中按下按钮时，在View Controller中更改UIView的颜色。

在我的UIViewController我有一个函数，当从集合视图控制器调用此函数时，该函数会更改颜色，但该函数会打印出来，但颜色不会更改。

查看控制器

 static let sharedInstance = UIStoryboard(name: "Main", bundle: nil).instantiateViewControllerWithIdentifier("settingPageId") as! SettingsViewController

        @IBOutlet weak var TopView: UIView!

override func viewDidLoad() {
        super.viewDidLoad()

        let colorsViewController = storyboard?.instantiateViewControllerWithIdentifier("colorsViewCollection")
        self.addChildViewController(colorsViewController!)
        colorCollectionView.addSubview((colorsViewController!.view)!)
}

    func colorHasBeenSelected(){

            TopView.backgroundColor = UIColor.blackColor() // color is not changed if called from collection view
            print("colorHasBeenSelected") // it prints ok

        }

集合视图控制器

let settingPage = SettingsViewController.sharedInstance

override func viewWillAppear(animated: Bool) {
        super.viewWillAppear(animated)
        _ = settingPage.view // without it TopView returns nil
}

@IBAction func colorAction(sender: UIButton) {

settingPage.colorHasBeenSelected()
}

如何让UIView内的UIViewController更改UICollectionView的背景颜色？