title: Change CSS property from existing value with Stylus
body: <p>I have a set of styles like this one:</p>
  
  <pre><code>&amp;.blue
    background #189cd8
    &amp;:hover
      background lighten(#189cd8, 10%)
  </code></pre>
  
  <p>I wonder if it's possible not to set that color the second time for hover state but somehow take it from the parent, like <code>background lighten(parent(background), 10%)</code>? I know I can use variables but here I just want to refer to the color of parent so don't want to use them.</p>