How do I remove this from source code

Hello, this css shows in my source code.

<link rel='stylesheet' id='farbtastic-css' target='_blank' href='http://mysite.org/wp-admin/css/farbtastic.css?ver=1.3u1' type='text/css' media='all' />

I don't think Product theme uses it, how do I remove it? I checked header.php and don't see it. Thanks