很遗憾，您无法自定义警报视图的外观，也无法更改按钮文本颜色.

Unfortunately you cannot customize the appearance of alert views, it is impossible to change the buttons text color.

在UIAlertView Class中有明确提到参考:

UIAlertView 类旨在按原样使用，而不是支持子类化.此类的视图层次结构是私有的，并且不得修改.

The UIAlertView class is intended to be used as-is and does not support subclassing. The view hierarchy for this class is private and must not be modified.

更新:

问题是关于 iOS7，但现在 UIAlertView 已弃用，对于 UIAlertController，您可以简单地更改视图色调颜色:

The question was about iOS7, but now UIAlertView is deprecated, for UIAlertController you can simply change the view tint color:

    let alert = UIAlertController(title: "Gimme a break",
                                message: "For God sake its iOS7 question!",
                         preferredStyle: .alert)
    alert.view.tintColor = UIColor.red

检查这个问题也很有帮助:如何在 iOS9 中更改 UIAlertController 按钮文本颜色?

It is helpful also to check this question: How to change UIAlertController button text colour in iOS9?