title: C++ regex invalid character (colon)
body: <p>I have this line of code </p>
  
  <pre><code>regex rgx("([A-Z0-9#\:])");
  </code></pre>
  
  <p>And it keeps telling me that my colon is an invalid character. 
  Whether I escape or not.
  Any help?
  Thanks!</p>