Make navigation bar transparency and solid colour

step 1.

    self.navigationController.navigationBar.translucent = YES;

    [self navigationController].navigationBar.backgroundColor = [UIColor clearColor];
    self.navigationController.navigationBar.alpha = .9;

Step 2.

Set background colour for navigation controller

     [self.navigationController.navigationBar setBackgroundImage:[UIImage imageNamed:@"background.jpg"] forBarMetrics:UIBarMetricsDefault];