title: How to change NSTextField background color in NSPopOver
body: <p><img src="https://i.stack.imgur.com/HcLKr.png" alt="enter image description here"></p>
  
  <p>Mac OSX 10.10 Xcode 6.1</p>
  
  <p>I created a tableview in NSPopOver. 
  I try to change textfield's background color. Why? no effect.
  The tableview's highlight set to "regular". 
  which way can let me change textfields background color to white?</p>