I did something similar in my app (IOS 7). I used the following code:
NSDictionary * navBarTitleTextAttributes = @{ NSForegroundColorAttributeName : [UIColor whiteColor],
NSFontAttributeName: [UIFont systemFontOfSize:18.0f]
};
[[UINavigationBar appearance] setTitleTextAttributes:navBarTitleTextAttributes];
Actually it is pretty much the same code just with a different notation. But maybe it is working that way? Where do you set the appearance? I define it directly in the AppDelegate class.