我不知道如何在iOS9中更改pin颜色的代码（因为苹果最近更改了它的代码），而且我在Swift中还是新手，所以，我现在不知道如何在我的代码中集成pinTintColor。
请在下面找到我的代码：

import UIKit
import MapKit

class ViewController: UIViewController, MKMapViewDelegate {
    @IBOutlet var map: MKMapView!

    override func viewDidLoad() {
        super.viewDidLoad()

        let annotation = MKPointAnnotation()
        let latitude:CLLocationDegrees = 40.5
        let longitude:CLLocationDegrees = -74.6
        let latDelta:CLLocationDegrees = 150
        let lonDelta:CLLocationDegrees = 150
        let span:MKCoordinateSpan = MKCoordinateSpanMake(latDelta, lonDelta)
        let location:CLLocationCoordinate2D = CLLocationCoordinate2DMake(latitude, longitude)
        let region:MKCoordinateRegion = MKCoordinateRegionMake(location, span)

        map.setRegion(region, animated: false)

        annotation.coordinate = location
        annotation.title = "Niagara Falls"
        annotation.subtitle = "One day bla bla"
        map.addAnnotation(annotation)
    }

    func mapView(mapView: MKMapView, viewForAnnotation annotation: MKAnnotation) -> MKAnnotationView? {
        // simple and inefficient example

        let annotationView = MKPinAnnotationView()

        annotationView.pinColor = .Purple

        return annotationView
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}