lightbox Single Image Lightbox 'background' color opacity

Site URL: https://www.nancyturnersmith.com/

I have three images (below) on this Home page. When I click on them the color behind the image is  a bit transparent. I would like it to be solid.
I was told by SQSP Customer

Service that the opacity of this Lightbox is fixed .I guess it's at '0.9' or something to that effect.

I do have this code for the portfolio pages and it works fine.

.gallery-lightbox-background {
    background-color: #fffaef;
    opacity: 1.0;
}

Thanks for anyones help.
Best Wishes,

George

.gallery-lightbox-background {
    background-color: #fffeaf;
    opacity: 1.0;
}

Try that, hope it helps.