title: octave graph background color changing
body: <p>I need to change the figure background color in Octave. No idea how to do that. </p>
  
  <p>From this:</p>
  
  <p><img src="https://i.stack.imgur.com/aZLPJ.png" height="250"></p>
  
  <p>To this:</p>
  
  <p><img src="https://i.stack.imgur.com/PIxik.png" height="250"></p>