If you're still looking for a better answer, I just stumbled across this thread and found a great solution: UISearchBar text color change in iOS 7
If you look at the answer given by Sandeep-Systematix (not the accepted answer, but the answer right below), he mentions a really clean way to modify subviews in any class with this method:
[[UITextField appearanceWhenContainedIn:[UISearchBar class], nil] setTextColor:[UIColor blueColor]];
You can read more about this in Apple's documentation: https://developer.apple.com/library/ios/documentation/uikit/reference/UIAppearance_Protocol/Reference/Reference.html
That said, here's what you'll need to change the white, rounded background of the UITextField inside the UISearchBar:
[[UITextField appearanceWhenContainedIn:[UISearchBar class], nil] setBackgroundColor:[UIColor redColor]];
Now if you needed to create different UISearchBars with different styles, you would simply create a subclass of UISearchBar and you'd end up with something like this:
[[UITextField appearanceWhenContainedIn:[MyCustomSearchBar class], nil] setBackgroundColor:[UIColor redColor]];