Cant Change UIView Background Color From Black

I have a simple UIView subclass ... but the background remains black no matter what

Typically that sort of thing is because you have forgotten to set the UIView subclass's isOpaque to false. It is a good idea to do this in the UIView subclass's initializer in order for it to be early enough.

For example, here I've adapted your code very slightly. This is the complete code I'm using:

class MyView : UIView {
    private var spaceshipBezierPath: UIBezierPath{
        let path = UIBezierPath()
        // ... identical to your code
        return path
    }
    override func draw(_ rect: CGRect) {
        UIColor.red.setFill()
        spaceshipBezierPath.fill()
    }
}

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()        
        let v = MyView(frame:CGRect(x: 100, y: 100, width: 200, height: 200))
        self.view.addSubview(v)
    }
}

Notice the black background:

Now I add these lines to MyView:

override init(frame:CGRect) {
    super.init(frame:frame)
    self.isOpaque = false
}
required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}

See the difference that makes?