title: Seaborn pairplot hue parameter not working as expected
body: <p>If "C" was assigned as value for the "hue" parameter, it was expected Seaborn not displayed column "C". Am I wrong?</p>
  
  <pre><code>sns.pairplot(df, hue='C')
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/UnlkQ.png" rel="noreferrer"><img src="https://i.stack.imgur.com/UnlkQ.png" alt="enter image description here"></a></p>
  
  <p>DataFrame:</p>
  
  <p><a href="https://i.stack.imgur.com/1xeOV.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/1xeOV.jpg" alt="enter image description here"></a></p>