title: set color for each violin in violin plot
body: <p>I tried <code>violin</code> plot in Seaborn with different colors for each violin as: </p>
  
  <pre><code>sns.violinplot(x='type', y='den', data=mydf, ax=axes[0], color=['red','blue','yellow'])
  </code></pre>
  
  <p>however I got:</p>
  
  <blockquote>
    <p>ValueError: to_rgb: Invalid rgb arg "('red', 'blue', 'yellow')"
    could not convert string to float: red</p>
  </blockquote>