title: Overlaying/Superimposing plots in matplotlib
body: <p>I have three scatter plots, with marker colors as red, green and blue.</p>
  
  <p>The points are placed at the same position(x,y) in all the three plots but may have different marker size. </p>
  
  <p>I want to superimpose these three plots over each other such that each point has the 3 colors 'added'.</p>
  
  <p>For example: if a particular point has the same area in all three plots, it should appear white.</p>
  
  <p>I tried using <code>plt.scatter()</code> three times, but this results in one plot getting plotted over another, that is, the scatter plot plotted the last appears over those which were plotted before it.</p>
  
  <p>Any way to overcome this?</p>