title: How to get rid of faint borders in Stata -by()- graph
body: <p>When I plot graphs I usually need white background. 
  Sometimes the problem is to get rid of "faint" borders and it's not hard to get rid of them by playing with the plot options.</p>
  
  <p>However, I really cannot get rid of such borders when I plot a <code>by</code> graph.
  See for instance: </p>
  
  <pre><code>sysuse auto, clear
  hist mpg, by(foreign, plotregion(fcolor(white)) graphregion(fcolor(white) ifcolor(white) color(white) icolor(white)) bgcolor(white))
  </code></pre>
  
  <p>How to eliminate the lines around the two graphs here?
  Any suggestion is highly appreciated</p>