title: class labels in Pandas scattermatrix
body: <p>This question has been asked before, <a href="https://stackoverflow.com/q/21131707/1586229">Multiple data in scatter matrix</a>, but didn't receive an answer. </p>
  
  <p>I'd like to make a scatter matrix, something like <a href="http://pandas.pydata.org/pandas-docs/stable/visualization.html#scatter-plot-matrix" rel="noreferrer">in the pandas docs</a>, but with differently colored markers for different classes. For example, I'd like some points to appear in green and others in blue depending on the value of one of the columns (or a separate list).</p>
  
  <p>Here's an example using the Iris dataset. The color of the points represents the species of Iris -- Setosa, Versicolor, or Virginica.</p>
  
  <p><img src="https://i.stack.imgur.com/PnJB0.png" alt="iris scattermatrix with class labels"></p>
  
  <p>Does pandas (or matplotlib) have a way to make a chart like that?</p>