Change the green border for an embedded scanner (ZBar)

Question

So I have a ZBarView within a UIViewController (for an embedded scanner) and I was wondering how I could change the Green Border to have it something like this?

#import "ZBarSDK.h"

@interface ScanViewController : UIViewController <ZBarReaderViewDelegate>
@property (nonatomic, strong) IBOutlet ZBarReaderView *readerView;
@property (strong, nonatomic) IBOutlet UILabel *scannedMachineLabel;
@end


- (void)viewDidLoad
{
    [super viewDidLoad];

    _readerView.readerDelegate = self;
    // ensure initial camera orientation is correctly set
    UIApplication *app = [UIApplication sharedApplication];
    [_readerView willRotateToInterfaceOrientation: app.statusBarOrientation
                                        duration: 0];

}