Change white background in lightbox to solid black

Hi,
I would like to change the lightbox background color from white to a solid black. I tried the following code as shown in a previous support message, however it is only transparent. How would I change the following to make it solid black and/or to a darker transparency? Thank you!

This is the previous code I mentioned above:

.sl-overlay {
background: #000 !important;
}

• This topic was modified 4 years, 6 months ago by bellco12.
• This topic was modified 4 years, 6 months ago by bellco12.