title: How to change axis-label color in ggplot2?
body: <p>I have tried</p>
  
  <pre><code>... + xlab("New label", colour="darkgrey")
  </code></pre>
  
  <p>and</p>
  
  <pre><code>... + xlab("New label", color="darkgrey")
  </code></pre>
  
  <p>But it says this argument is unused. I look into <code>?xlab</code>, but it doesn't include any color parameter. Is it possible to change it? How?</p>