title: Change background color of cell based on time passed after edit in Google Sheets
body: <p>I think this would be a neat feature that could be applied to many spreadsheets in Google Doc, I just don't know how to do it.</p>
  
  <p>The general idea would to highlight cells that have been recently edited and have them change back to a neutral background color (or no color) after a set time.</p>
  
  <p>To me (and probably others) this would be extremely useful to quickly view a spreadsheet and see what has been recently changed.</p>
  
  <p>Ideally I would make it so that a cell edited within the past 2 hours would be light green, 12 hours be  light yellow, and 48 hours be light red, and anything after that would reset the background color.</p>
  
  <p>Any ideas to make this happen? Thanks!</p>