Change Color of MPVolumeView Route Button iOS 7

Question

I am designing a Music app for iOS 7 and I want to put the "AirPlay" route selector button directly in my app. I am able to get the button placed just fine, however it doesn't show up because the icon is white and my background is white.

Is there a way to change the color of the Route Button?

Here is the code I'm using to create the button.

self.airPlayButton = [[MPVolumeView alloc] initWithFrame:CGRectZero];
    self.airPlayButton.showsVolumeSlider = NO;
    [self.airPlayButton sizeToFit];
    self.airPlayButton.backgroundColor = [UIColor myGreenColor];
    [self addSubview:self.airPlayButton];

Basically the picture below is what I want, except I want the icon green instead of just it's background.

Answer 1

in reviewing Adams answer I like more clarity in that task. So I safe-guarded that code a bit:

Objective-C:

for( UIView *wnd in volumeView.subviews ) {
    if( [wnd isKindOfClass:[UIButton class] ]) {
        UIButton *button = (UIButton*) wnd;
        UIImage *img = button.currentImage;
        UIImage *img2 = [img imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];
        [volumeView setRouteButtonImage: img2 forState:UIControlStateNormal];
        break;
    }
}

Swift:

    for view in volumeView.subviews {
        if view.isKindOfClass(UIButton) {
            let buttonOnVolumeView : UIButton = view as! UIButton
            volumeView.setRouteButtonImage(buttonOnVolumeView.currentImage?.imageWithRenderingMode(.AlwaysTemplate), forState: .Normal)
            break;
        }
    }

Now it reacts on the tintColor property of volumeView and if Apple decides to add another button or change the sequence this code will still work.

Answer 2

To expand on lanbo's answer, you can also get the original image of the Route Button and create a copy that uses the UIImageRenderingMode.AlwaysTemplate rendering mode. That way it heeds the current tintColor.

In Swift:

    let volumeView = MPVolumeView()

    if let routeButton = volumeView.subviews.last as? UIButton,
        let routeButtonTemplateImage  = routeButton.currentImage?.imageWithRenderingMode(.AlwaysTemplate)
    {
        volumeView.setRouteButtonImage(routeButtonTemplateImage, forState: .Normal)
    }