UIButton突出显示淡入淡出效果，例如Apple Mail应用程序

Question

In the Apple Mail app, if you open a message and tap on the sender or a recipient, there is a nice fade in/out effect for the highlighted state.

How can this effect be created?

I've already tried overriding UIButton setHighlighted and using setTitleColor:forState:

-(void)setHighlighted:(BOOL)highlighted
{
    if (highlighted) {
        self.backgroundColor = [UIColor darkGrayColor];
    } else {
        self.backgroundColor = [UIColor clearColor];
    }

    [super setHighlighted:highlighted];
}

...
[button setTitleColor:[UIColor blueColor] forState:UIControlStateHighlighted];