title: How to reset background color of a python tkinter button?
body: <p>Simple question, have parsed numerous search results, haven't found a simple answer.  I set a very urgent button to red if something is not found so users click it first.  Once clicked, I want to set the background back to normal like <code>button.config(bg='')</code>.  I tried 'grey' but it's not the right color.</p>
  
  <p>What do I set it to?  </p>