title: Hex colors: Numeric representation for "transparent"?
body: <p>I am building a web CMS in which the user can choose colours for certain site elements.
  I would like to convert all colour values to hex to avoid any further formatting hassle ("rgb(x,y,z)" or named colours). I have found a good JS library for that.</p>
  
  <p>The only thing that I can't get into hex is "transparent". I need this when explicitly declaring an element as transparent, which in my experience can be different from not defining any value at all.  </p>
  
  <p>Does anybody know whether this can be turned into some numeric form? Will I have to set up all processing instances to accept hex values <em>or</em> "transparent"?  I can't think of any other way.</p>