在tabBarcontroller的.m文件中

+ (void)initialize
{
    // 通过appearance统一设置所有UITabBarItem的文字属性
    // 后面带有UI_APPEARANCE_SELECTOR的方法, 都可以通过appearance对象来统一设置
    NSMutableDictionary *attrs = [NSMutableDictionary dictionary];
    attrs[NSFontAttributeName] = [UIFont systemFontOfSize:12];
    attrs[NSForegroundColorAttributeName] = [UIColor grayColor];
    
    NSMutableDictionary *selectedAttrs = [NSMutableDictionary dictionary];
    selectedAttrs[NSFontAttributeName] = attrs[NSFontAttributeName];
    selectedAttrs[NSForegroundColorAttributeName] = [UIColor darkGrayColor];
    
    UITabBarItem *item = [UITabBarItem appearance];
    [item setTitleTextAttributes:attrs forState:UIControlStateNormal];
    [item setTitleTextAttributes:selectedAttrs forState:UIControlStateSelected];
}

去除图片的蓝色渲染效果: 在传入的image时 后边加上mageWithRenderingMode:UIImageRenderingModeAlwaysOriginal

 vc.tabBarItem.image = [[UIImage imageNamed:image]imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];

例如:

- (void)setupChildVc:(UIViewController *)vc title:(NSString *)title image:(NSString *)image selectedImage:(NSString *)selectedImage{
    vc.navigationItem.title = title;
    vc.tabBarItem.title = title;
    vc.tabBarItem.image = [[UIImage imageNamed:image]imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
    vc.tabBarItem.selectedImage = [[UIImage imageNamed:selectedImage]imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
    UINavigationController * nv = [[UINavigationController alloc]initWithRootViewController:vc];
    
    
    [self addChildViewController:nv];
    
    
    
}