Change background top header when scrolled

Hi!

I’ve changed the background color of the top header:

#top #header_meta {
background-color: rgba(0, 141, 156, 0.7) !important;
}

Now I want the color to be not transparant when scrolled. How can I do that? I’ve added the code below, but the code above is overriding it.

.av_header_sticky #header_meta {
background-color: #008d9c !important;
}

See private content for url. The 3 buttons at the top right must remain fully visible, not transparent!

Thanks a lot!