AppDelegate.swift

import Cocoa

class AppDelegate: NSObject, NSApplicationDelegate {
                            
    @IBOutlet var window: NSWindow

    func applicationDidFinishLaunching(aNotification: NSNotification?) {
        var frame = NSMakeRect(0, 0, 200, 200)
        var window = NSWindow(contentRect:frame, styleMask:NSBorderlessWindowMask, backing:NSBackingStoreType.Buffered, defer:false)
        // This doesn't seem to have an effect. :/
        window.backgroundColor = NSColor.blueColor()
        window.makeKeyAndOrderFront(self)
    }

}