title: BASH: Search for several Keywords in file and highlight them
body: <p>I want to search all files in a directory for a Keyword and color it, like:</p>
  
  <pre><code>grep -n "keyword1" * --color
  </code></pre>
  
  <p>Now I want to highlight all occurrences of <code>keyword2</code> and <code>keyword3</code> in an other color.</p>
  
  <p>I managed</p>
  
  <pre><code>grep -n "keyword1 * |egrep --color "keyword2|keyword3|$'
  </code></pre>
  
  <p>this will color both last keywords but in the same color.
  but I fail to set several different colors to work with a coloring from the first grep-statement. I don't know how to set the constant <code>GREP_COLORS</code> correctly</p>