The question is similar to iOS 8 UIActivityViewController and UIAlertController button text color uses window's tintColor but in iOS 9.
I have a UIAlertControlle
In Swift 3.x:
I found the following to work effectively. I call this at app launch .
UIView.appearance(whenContainedInInstancesOf: [UIAlertController.self]).tintColor = UIColor.black
So this would change the tint color of all UIAlertViewController button labels in your app globally. The only button label color it doesn't change are those which have a UIAlertActionStyle of destructive.