To change the background color of tab bar, we can change the tab bar setting in storyboard.
However, unlike navigation bar, we cannot setting the tab bar item's tint color inside storyboard.
We have to add some code in the app delegate, inside application:didFinishLaunchingWithOptions:, add
[[UITabBar appearance] setTintColor:[UIColor yellowColor]];
Note that this is an application-wide setting, all tab bar items will tint to the specific color.34