Page Hero, Background Overlay Graduation

Hi guys.
I the first post form me.

A question about Page Hero Header:

I have set an Element to show a featured Image of each post.
I need to add a background overlay, and take a look at css, it add a background-image as graduation from and to the same color. But If I want to set. graduation from 1 to 0 of that color?
Or if I want to change the value of this graduation? I can set it onto css, but it hide the featured image set.
There is an hook for that?

Thanks for your time