UINavigationBar更改默认样式

改NavigationBar的颜色，UIAppearance里面改TintColor而不是backgroundColor
[[UINavigationBar appearance] setBarTintColor:[UIColor blackColor]];

改NavigationItem的颜色，
self.navigationController.navigationBar.tintColor = [UIColor greenColor];
OR
self.window.tintColor = [UIColor redColor]
第二种同时修改navigationitem和tabbaritem的选中颜色

改NavigationBar Title的颜色，
[[UINavigationBar appearance]setTitleTextAttributes:@{NSForegroundColorAttributeName:[UIColor whiteColor]}];
self.navigationController?.navigationBar.titleTextAttributes = [NSForegroundColorAttributeName:UIColor.whiteColor()]

让backbutton title消失
[[UIBarButtonItem appearance] setBackButtonTitlePositionAdjustment:UIOffsetMake(0, -60) forBarMetrics:UIBarMetricsDefault];