Resolved Overlay colour

I try it but without success

In custom css file and template this:
.hero-section {
background-color: transparent;
background-blend-mode: normal; }

and this:

hero-section {
background-color: transparent;
background-blend-mode: normal; }

In our demo that Row had a different class name, that's why.

The proper code should be

.sppb-slider-wrapper.sppb-slider-fullwidth-wrapper .sppb-slide-item-bg {

    background-color: transparent;

background-blend-mode: normal; 

}

I added in Page > Custom CSS

---
I updated the manual, as well.

Tnx Paul

Have nice day!

You're welcome.
Have a nice weekend, go away beyond the computer, take fresh air, enjoy nature.