更改图钉颜色 MKMapView

我以这种方式向地图添加注释：

MyAnnotation *annotationPoint2 = [[MyAnnotation alloc] init];
annotationPoint2.coordinate = anyLocation;
annotationPoint2.title = [NSString stringWithFormat:@"%@", obj];
annotationPoint2.subtitle = @"";  //or set to nil
annotationPoint2.keyValue = [NSString stringWithFormat:@"%@", key];
[mapPins addAnnotation:annotationPoint2];

引脚都是红色的，我希望它们都是绿色的。我怎样才能改变颜色？我已经尝试了以下方法，但仍然出现红色标记：

annotationPoint2.pinColor = MKPinAnnotationColorGreen;

- (MKAnnotationView *) mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>) annotation 
  {
    MKPinAnnotationView *annView=[[MKPinAnnotationView alloc]initWithAnnotation:annotation reuseIdentifier:@"pin"];
    annView.pinColor = MKPinAnnotationColorGreen;
    return annView;
  }