Possible to reduce ALL black background transparencies? sitewide?

I asked this in an old resolved thread. Figured I start a separate one instead.

How can I reduce the transparency of ALL the black backgrounds sitewide? I’d like to reduce them from 0.8 down to maybe 0.6 or maybe more.

I’m talking mainpage/homepage/frontpage header (the one with the title/logo and menu at the top of the slider page), the black background behind posts, the black background behind the sidebar widget area, the black background behind the footer.

You know, EVERYWHERE there’s a semi-transparent black background.

Thank you.