title: how to calculate color difference in percentage for Less
body: <p>Say i have two colors <code>#595b5c</code> and <code>#424545</code>. I want to know the percentage difference between them, how to do that? The reason being i want to use <a href="http://lesscss.org/functions/#color-operations-lighten">lighten</a> and <a href="http://lesscss.org/functions/#color-operations-darken">darken</a> functions of less which take percentage as a parameter.</p>
  
  <p>Eg: </p>
  
  <pre><code>@darkgrey1: #595b5c;
  @darkgrey2: darken(@darkgrey1,10%);
  </code></pre>
  
  <p>How do i know by how much percent <code>#424545</code> is darker than <code>#595b5c</code></p>