How to change inactive icon/text color on tab bar?

for changing color of unselect icons of tabbar

For below iOS 10:

// this code need to be placed on home page of tabbar    
for(UITabBarItem *item in self.tabBarController.tabBar.items) {
    item.image = [item.image imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
}

Above iOS 10:

// this need to be in appdelegate didFinishLaunchingWithOptions
[[UITabBar appearance] setUnselectedItemTintColor:[UIColor blackColor]];

In every first ViewController for each TabBar:

- (void)viewDidLoad
{
    [super viewDidLoad];

    // changing the unselected image color, you should change the selected image 
    // color if you want them to be different
    self.tabBarItem.selectedImage = [[UIImage imageNamed:@"yourImage_selectedImage"]
    imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];

    self.tabBarItem.image = [[UIImage imageNamed:@"yourImage_image"] 
    imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
}

The clue of this code is 'UIImageRenderingModeAlwaysOriginal':

Rendering Modes by Apple Documentation:

UIImageRenderingModeAutomatic,          // Use the default rendering mode for the context where the image is used    
UIImageRenderingModeAlwaysOriginal,     // Always draw the original image, without treating it as a template
UIImageRenderingModeAlwaysTemplate,     // Always draw the image as a template image, ignoring its color information

To change text color:

In AppDelegate:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // Add this if you only want to change Selected Image color 
    // and/or selected image text
    [[UITabBar appearance] setTintColor:[UIColor redColor]];

    // Add this code to change StateNormal text Color,
    [UITabBarItem.appearance setTitleTextAttributes:
    @{NSForegroundColorAttributeName : [UIColor greenColor]} 
    forState:UIControlStateNormal];

    // then if StateSelected should be different, you should add this code
    [UITabBarItem.appearance setTitleTextAttributes:
    @{NSForegroundColorAttributeName : [UIColor purpleColor]} 
    forState:UIControlStateSelected];

    return YES;
}

You can also set the property Render As of your tab bar images within your asset catalog directly. There you have the option to set the property to Default, Original Image and Template Image.