title: How to do a scatter plot with empty circles in Python?
body: <p>In Python, with Matplotlib, how can a scatter plot with <em>empty</em> circles be plotted?  The goal is to draw empty circles around <em>some</em> of the colored disks already plotted by <code>scatter()</code>, so as to highlight them, ideally without having to redraw the colored circles.</p>
  
  <p>I tried <code>facecolors=None</code>, to no avail.</p>