I am trying to add a file which is located in sites/default/files/color/theme-768/color.css using drupal_add_css().

I have tried drupal_add_css($filepath), but it doesn't work. I tried putting it in template.php and hook_init(), but still it isn't included in the style tags of head section or anywhere.

How I do include a CSS file like this using drupal_add_css()?