Change overlay color and opacity on Fancybox lightbox

Hi,

This is a great plugin, it works fantastic and it will be a great addition to my WordPress Portfolio site! I was wondering what the process might be to change the overlay color and opacity on the Fancybox lightbox. I tried for quite some time to find a place within the CSS files and also searched quite extensively on the web but no luck. I sure hope that you can help. Thanks in advance!!