Adding an overlay to a WordPress theme

Good evening
I am running a Studiopress theme called showcase pro, and I would like all page headers to be the same as the featured front page.

How can I do this, I have an image with a blue overlay on the Home page, is there anyway to can do this on all pages.

I have attached an image with the overlay, and one that is not, so you can see my issue I am having.

Thanks
Andrew