title: Color stamping dates for multiple scatter plots in Matplotlib
body: <p>I have 3 dataframes that have 3 features I'd like to map into scatter plots:</p>
  
  <pre><code>Date  Energy  Cost
  </code></pre>
  
  <p>I need to create a series of scatter plots that plot Energy and Cost but color coded by the year in the date column.</p>
  
  <p>The dates are in datetime format and go for 4 years and look like:</p>
  
  <pre><code>2015-12-30 00:00:00
  2016-20-12 00:00:00
  etc...
  </code></pre>
  
  <p>I know I can plot <code>plt.scatter(data[:], data[:].... c=data[:])</code></p>
  
  <p>But cannot figure how to properly format it specifically for intervals of time so that each color is different for each of the 4 years.</p>