title: Bokeh circle plot color in ColumnDataSource
body: <p>I am trying to display my clusters in an interactive circle plot with Bokeh. I managed to display the plot itself, but all the specs on the graph are blue. I want to display them in 4 clusters, since this is a cluster analyses. </p>
  
  <p>This is the code that works without the implementation of color:</p>
  
  <pre><code>colormap = {0: 'brown', 1: 'green', 2: 'blue', 3: 'purple'}
  colors = [colormap[x] for x in df['cluster']]
  
  source = ColumnDataSource(data=df)
  hover = HoverTool(tooltips=[('index', '@index'),('Tweets','@Bericht'), ('Polarity','@Polarity'), ('Subjectivity','@Subjectivity')])
  
  p = figure(title = "Sentiment analyse", plot_width=1000, plot_height=500)
  p.xaxis.axis_label = 'Polarity'
  p.yaxis.axis_label = 'Subjectivity'
  
  p.circle(x='Polarity', y='Subjectivity', source=source, fill_alpha=0.2, size=6)
  
  p.add_tools(hover)
  
  
  
  output_file("sentiment.html", title="sentiment.py example")
  
  show(p)
  </code></pre>
  
  <p>When adding the color attribute <code>color=colors</code> in <code>p.circle</code>, I get an error because I need to implement the color in the <code>source = ColumnDataSource(data=df)</code>.</p>
  
  <p>Does anyone know how to implement this <code>colors</code> attribute in the <code>ColumnDataSource</code>?</p>