[UIViewController fubar] -- method to recursively color the view hierarchy

gistfile1.m

- (void)fubar
{
    [self fubarWithViews:self.view.subviews];
}
- (void)fubarWithViews:(NSArray *)views
{
    for (UIView *view in views) {
        CGFloat hue = ( arc4random() % 256 / 256.0 );  //  0.0 to 1.0
        CGFloat saturation = ( arc4random() % 128 / 256.0 ) + 0.5;  //  0.5 to 1.0, away from white
        CGFloat brightness = ( arc4random() % 128 / 256.0 ) + 0.5;  //  0.5 to 1.0, away from black
        UIColor *color = [UIColor colorWithHue:hue saturation:saturation brightness:brightness alpha:1];

        [view setBackgroundColor:[color colorWithAlphaComponent:0.4]];
        
        [self fubarWithViews:view.subviews];
    }
}

Reference for generating a random color: https://gist.github.com/kylefox/1689973