title: matplotlib not changing scatter point colors if they are assigned the first time
body: <p>In the following minimal example, I create 1-point scatter plot and later change color of points in loop using <a href="http://matplotlib.sourceforge.net/api/collections_api.html#matplotlib.collections.Collection.set_color" rel="nofollow">Collection.set_color</a>. If I set the color(s) the first time <a href="http://matplotlib.sourceforge.net/api/pyplot_api.html#matplotlib.pyplot.scatter" rel="nofollow">scatter</a> is called, <code>set_color</code> will not change its face color (only edge color), whereas if I don't specify it when the scatterplot is created, face color will change according to <code>set_color</code>.</p>
  
  <pre><code>from pylab import *
  from numpy import *
  coll=scatter([0],[0],s=500,c=[.1]) # omit c=[.1] here to have face color changing later
  ion(); show()
  for a in linspace(.1,.9):
      coll.set_color(coll.get_cmap()(a))
      draw()
  </code></pre>
  
  <p>Is that a bug, or am I missing something in the documentation?</p>