Opacity background Hero block

Hello, I don’t find how to adjust the opacity of the background in the Hero header, I have selected darken and try to make a class, but it don’t work.

Now I’m adjusting this directly in the style.css file but when I update the site I have to re-change it.

The class in css are .texture-darken::before in line 146.

any help would be nice.

Thank you

if you’ve already created custom class for the hero header, click the custom class and choose the paint brush icon and then the color option, inside this option you can adjust the opacity for both color background of photo background.17 AM54 AM