iphone - UIViewAnimationTransitionCurDown\Up

Question

[UIView beginAnimations:@"Animate" context:nil];
[UIView setAnimationDuration:0.75];
[UIView setAnimationCurve:UIViewAnimationCurveEaseOut];

[UIView setAnimationTransition:UIViewAnimationTransitionCurlDown forView:self.view cache:YES];

[aViewController viewWillDisappear:YES];
[bViewController viewWillAppear:YES];

[aViewController.view removeFromSuperview];
[self.view addSubview:bViewController.view];


[aViewController viewDidDisappear:YES];
[bViewController viewDidAppear:YES];

[UIView commitAnimations];

ページを上下に移動すると、最初のページの裏が見えます。問題は、ページの裏側の色を変更したいです。どうすれば対処できますか？