No "use background color as overlay option" available

Hi there,
I am using GP and Beaver Builder. I am beginning work on a site here
http://www.celtic.manselldesign.ca/
and I am trying to use a colour overlay over the header image. I have seen an instructional video here https://www.youtube.com/watch?v=GxNg9lrdbeg which shows the option to use the background image as an overlay however that option is not appearing for me in the admin. Any advice would be appreciated.
Thanks