一、如果只是设置选中状态的字体颜色，使用 tintColor 就可以达到效果
- self.tabBar.tintColor = [UIColor redColor];
二、但如果要将未选中状态和选中状态下的颜色都改变，可以使用 setTitleTextAttributes:<#(nullable
NSDictionary<NSString *,id> *)#>
forState:<#(UIControlState)#> 达到效果
- [nav.tabBarItem setTitleTextAttributes:@{NSForegroundColorAttributeName:[UIColor redColor]} forState:UIControlStateNormal];
- [nav.tabBarItem setTitleTextAttributes:@{NSForegroundColorAttributeName:[UIColor blueColor]} forState:UIControlStateSelected];
或者
- [[UITabBarItem appearance] setTitleTextAttributes:@{NSForegroundColorAttributeName:[UIColor redColor]} forState:UIControlStateNormal];
- [[UITabBarItem appearance] setTitleTextAttributes:@{NSForegroundColorAttributeName:[UIColor blueColor]} forState:UIControlStateSelected];
UITabBar 设置选中、未选中状态下title的字体颜色
原文：https://www.cnblogs.com/Free-Thinker/p/9210865.html
