title: In Javascript Regex, how do I validate that a string is a valid hexadecimal colour?
body: <p>Given a string like <code>#fff443</code> or <code>#999999</code></p>
  
  <p>How do I verify that the string has:</p>
  
  <ul>
  <li>7 characters, with the first one being a hash</li>
  <li>no symbols in the string besides the hash in the beginning</li>
  </ul>