When you specify a tint for a view, the tint is automatically propagated to all subviews in the view’s hierarchy. Because UIWindow inherits from UIView, you can specify a tint color for the entire app by setting the window’s tint property using code like this:
Under application:didFinishLaunchingWithOptions:
window.tintColor = [UIColor purpleColor];
Source - iOS Transitions . Check it out under Using Tint Color section