If you just want to use a solid navigation bar color and have set this up in your storyboard, use this code in your
AppDelegate
class to remove the 1 pixel border via the appearance proxy:
[[UINavigationBar appearance] setBackgroundImage:[[UIImage alloc] init]
forBarPosition:UIBarPositionAny
barMetrics:UIBarMetricsDefault];
[[UINavigationBar appearance] setShadowImage:[[UIImage alloc] init]];