title: Set the color for scatter-plot with DataFrame.plot
body: <p>I am using python to plot a pandas DataFrame</p>
  
  <p>I set the color for plotting like this:</p>
  
  <pre><code>allDf = pd.DataFrame({
      'x':[0,1,2,4,7,6],
      'y':[0,3,2,4,5,7],
      'a':[1,1,1,0,0,0],
      'c':['red','green','blue','red','green','blue']
  },index = ['p1','p2','p3','p4','p5','p6'])
  
  allDf.plot(kind='scatter',x='x',y='y',c='c')
  plt.show()
  </code></pre>
  
  <p>However it doesn't work (every point has a blue color)</p>
  
  <p>If I changed the definition of DataFrame like this  </p>
  
  <pre><code>'c':[1,2,1,2,1,2]
  </code></pre>
  
  <p>It appears color but only black and white, I want to use blue, red and more...</p>