title: Several pin colors on same map in MKMapView
body: <p>I have a <code>MKMapView</code> in my app with several pins on it and I'd like to set different colors for each pin. My view controller is implementing <code>MKMapViewDelegate</code> and I've defined viewForAnnotation method.</p>
  
  <pre><code>- (MKAnnotationView *) mapView:(MKMapView *)mapView 
  viewForAnnotation:(id &lt;MKAnnotation&gt;) annotation {
      MKPinAnnotationView *annView=[[MKPinAnnotationView alloc] 
          initWithAnnotation:annotation reuseIdentifier:@"pin"];
      annView.pinColor = MKPinAnnotationColorGreen;
      return annView;
  }
  </code></pre>
  
  <p>It works fine and changes pin color to green. However the color is changed for all pins and I'd like to color them with several colors (based on some criteria I'd define, lets assume I want to have odd pins green and even pins yellow or something as simple as that). How can this be achieved?</p>