title: Displaying PCA with different colors
body: <p>I have this data:</p>
  
  <pre><code>Desc     ALL1  ALL2  AML1  AML2
  Gene1    -214  -342    87  -172
  Gene2    -153  -200  -248  -122
  Gene3    -58    41    262   38
  Gene4     88    328   295   31
  </code></pre>
  
  <p>We have two types of tissues AML and ALL lukemia
  I want to apply PCA to this data, so I tried doing this:</p>
  
  <pre><code>pca &lt;- prcomp(x = all_aml_train_gct)
  </code></pre>
  
  <p>Now I want to plot it:</p>
  
  <pre><code>biplot(fit)
  </code></pre>
  
  <p>I get something like this:
  <a href="https://i.stack.imgur.com/IEVcQ.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/IEVcQ.png" alt="test plot"></a></p>
  
  <p>How can I color the plot to distinguish ALL and AML?</p>