fix

iOSClient/AppDelegate.m

@@ -118,7 +118,8 @@ PKPushRegistry *pushRegistry;
     [[UINavigationBar appearance] setBackgroundImage:[[UIImage alloc] init] forBarPosition:UIBarPositionAny barMetrics:UIBarMetricsDefault];
     [[UINavigationBar appearance] setShadowImage:[[UIImage alloc] init]];
     [UINavigationBar appearance].translucent = NO;
-
+    [[UIView appearanceWhenContainedInInstancesOfClasses:@[[UIAlertController class]]] setTintColor:[UIColor blackColor]];
+    
     // passcode
     [[BKPasscodeLockScreenManager sharedManager] setDelegate:self];