Using CAPTCHA with a Theme

I am trying to change the background color of the CAPTCHA to match my theme. I know I can change it globally in SiteController.php by changing the backColor to the captcha array. Searching through the forum I found this solution from an older thread (http://www.yiiframework.com/forum/index.php?/topic/10588-customizing-captchas/):


you can load a theme-config, however, based on your current theme string


public function actions()

{

    return array(

        'captcha'=> include ($path.to.themeConfig)

    );

}

Does this function get added into SiteController.php? Does just the backColor need to be in this theme-config? Where should the theme-config be located?