How to change tintColor of UIBarButtonItem? [SWIFT]

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {

// Changing the status bar's colour to white
UIApplication.sharedApplication().statusBarStyle = .LightContent

// Changing the navigation controller's background colour
UINavigationBar.appearance().barTintColor = UIColor(red: 0.0/255.0, green: 165.0/255.0, blue: 227.0/255.0, alpha: 1.0)

// Changing the navigation controller's title colour
UINavigationBar.appearance().titleTextAttributes = [NSForegroundColorAttributeName: UIColor.whiteColor()]

// Changing the colour of the bar button items
UINavigationBar.appearance().tintColor = UIColor.whiteColor()

// Changing the tint colour of the tab bar icons
UITabBar.appearance().tintColor = UIColor(red: 0.0/255/0, green: 165.0/255.0, blue: 227.0/255.0, alpha: 1.0)

return true
}