请问怎么自定义工具栏配色

如题，怎么自定义QLPreviewController的navBar 和工具条的 tintColor

QLPreviewController * preview = [[QLPreviewController alloc] init];
preview.dataSource = self;
preview.currentPreviewItemIndex = sender.tag;
preview.editing= YES; 
[self presentModalViewController:preview animated:YES];
[preview release];

下面这两行代码我加上之后没有用

[preview.tabBarController.tabBar setTintColor:[UIColor blackColor]];
[preview navigationController].navigationBar setTintColor: [UIColor blackColor]];