title: Preserve colouring after piping grep to grep
body: <p>There is a simlar question in <a href="https://stackoverflow.com/questions/867877/preserve-ls-colouring-after-greping">Preserve ls colouring after grep’ing</a> but it annoys me that if you pipe colored grep output into another grep that the coloring is not preserved.</p>
  
  <p>As an example <code>grep --color WORD * | grep -v AVOID</code> does not keep the color of the first output. But for me <code>ls | grep FILE</code> do keep the color, why the difference ?</p>