changing the tint color of navigation bar changes the size of the view

Question

I have a tabbar based application in which the controller of each tabbar item is navigation controller. on the navigation controller I have an image view(added by the code) starting just below the navigation bar. The problem is when i changes the tint color of the navigation bar as

self.navigationController.navigationBar.tintColor = [UIColor redColor];

The tint color of the bar changes but the gap between the navBar and the imageview increases.The gap seems to be equal the height of the navigation bar.But if i keep the navBar color to be defaul averything seems to be perfect.