iOS7 introduced general tint-color. I think UIAlertView is also in the valid range, but actually tintColor doesn\'t look to work with UIAlertView.
The previous answers mentioning [[UIView appearance] setTintColor:[UIColor redColor]]; should work but this code is doing way more than if should if you want to change only the UIAlertView tint color.
You can aim the component this way on iOS < 9 :
[[UIView appearanceWhenContainedIn:[UIAlertView class], nil] setTintColor:[UIColor redColor]];
[[UIView appearanceWhenContainedIn:[UIAlertController class], nil] setTintColor:[UIColor redColor]];
And on iOS >9 :
[[UIView appearanceWhenContainedInInstancesOfClasses:@[[UIAlertView class]]] setTintColor:[UIColor redColor]];
[[UIView appearanceWhenContainedInInstancesOfClasses:@[[UIAlertController class]]] setTintColor:[UIColor redColor]];