title: Cocoa OS X - Change background of window in Swift
body: <p>I am making an app for OS X with Cocoa with Xcode and I want to change the Windows background color with alpha in swift. I don't know how to call the window from the code and how to set its background color with alpha value. How can I do that?</p>
  
  <p>Here is my app delegate class, with hierarchy:</p>
  
  <p><a href="https://i.stack.imgur.com/toPdP.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/toPdP.png" alt="enter image description here"></a></p>