title: How to remove outline of circle marker when using pyplot.plot in matplotlib
body: <p>I'm producing a scatter plot using pyplot.plot (instead of scatter - I'm having difficulties with the colormap)</p>
  
  <p>I am plotting using the 'o' marker to get a circle, but the circle always has a black outline.</p>
  
  <p>How do I remove the outline, or adjust its colour?</p>