Swift – setup more than one fillColor in MKCircle

Question

I'm trying to have my MKCircle fillColor change when the markerType is different. For example, if the markerType is "airport", then the fill should be red, and if it is "Sea Plane Base" then the fill should be black.

// MARK: Radius overlay
func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
    if overlay is MKCircle {
        let circle = MKCircleRenderer(overlay: overlay)

        for markerType in airports {
            if markerType.markerType == "airport" {
                circle.strokeColor = UIColor.red
                circle.fillColor = UIColor(red: 255, green: 0, blue: 0, alpha: 0.1)
                circle.lineWidth = 1
            } else {
                circle.strokeColor = UIColor.black
                circle.fillColor = UIColor(red: 0, green: 0, blue: 0, alpha: 0.1)
                circle.lineWidth = 1
            }
        }

        return circle
    } else {
        return MKPolylineRenderer()
    }
}

I'm using this function to show the radius.

func mainAirportRadius(radius: CLLocationDistance) {
    //MARK: Airport location
    for coordinate in airports {
        let center = coordinate.coordinate
        let circle = MKCircle(center: center, radius: radius)
        mapView.add(circle)
    }
}

Then I call it in the viewDidLoad method

mainAirportRadius(radius: 8046.72)