它将通过-(void)viewDidLoad中的这一行来解决:

self.navigationItem.backBarButtonItem.tintColor = UIColor.whiteColor;

让我们试试这段代码:

 func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    // Override point for customization after application launch.

    let navigationBarAppearace = UINavigationBar.appearance()
    navigationBarAppearace.tintColor = UIColor.whiteColor()  // Back buttons and such
    navigationBarAppearace.barTintColor = UIColor.purpleColor()  // Bar's background color
    navigationBarAppearace.titleTextAttributes = [NSForegroundColorAttributeName:UIColor.whiteColor()]  // Title's text color

    self.window?.backgroundColor = UIColor.whiteColor()
    return true
}

你应该这样使用:

navigationController?.navigationBar.barTintColor = .purple
navigationController?.navigationBar.tintColor = .white

在Swift 4中，你可以使用以下方法来解决这个问题:

let navStyles = UINavigationBar.appearance()
// This will set the color of the text for the back buttons.
navStyles.tintColor = .white
// This will set the background color for navBar
navStyles.barTintColor = .black

在Swift3中，将后退按钮设置为红色。

self.navigationController?.navigationBar.tintColor = UIColor.red

你应该加上这一行

 self.navigationController?.navigationBar.topItem?.backBarButtonItem?.tintColor = .black