There are many way to do, I show a trick, don’t follow me :D

extension UIApplication {
  class func setStatusBarBackgroundColor(color: UIColor) {
        guard let statusBar = UIApplication.sharedApplication().valueForKey("statusBarWindow")?.valueForKey("statusBar") as? UIView else { return }
        statusBar.backgroundColor = color
    }
}

Do and see the change:

UIApplication.setStatusBarBackgroundColor(.grayColor())