如何在不更改Swift默认位置引脚的情况下更改MapKit中的markerTintColor？

import MapKit

class CustomAnnotationView: MKAnnotationView {
    override init(annotation: MKAnnotation?, reuseIdentifier: String?) {
        super.init(annotation: annotation, reuseIdentifier: reuseIdentifier)
        self.markerTintColor = UIColor.red // 设置默认颜色
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
    
    override func setSelected(_ selected: Bool, animated: Bool) {
        super.setSelected(selected, animated: animated)
        if selected {
            self.markerTintColor = UIColor.blue // 设置选中颜色
        } else {
            self.markerTintColor = UIColor.red // 恢复默认颜色
        }
    }
}

class ViewController: UIViewController, MKMapViewDelegate {
    @IBOutlet weak var mapView: MKMapView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        mapView.delegate = self
    }
    
    func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {
        if annotation is MKUserLocation {
            return nil
        }
        
        let reuseIdentifier = "CustomAnnotation"
        var annotationView = mapView.dequeueReusableAnnotationView(withIdentifier: reuseIdentifier)
        
        if annotationView == nil {
            annotationView = CustomAnnotationView(annotation: annotation, reuseIdentifier: reuseIdentifier)
        } else {
            annotationView?.annotation = annotation
        }
        
        return annotationView
    }
}