That widget area is setup just like the other widget areas that use Background Images. The black color you see is actually an image. There are multiple ways to remove it, but the fastest way is by adding some CSS to override it –
.front-page-4 {
background-color: #fff;
background-image: none !important;
}
You can change the color to whatever you want, I just added #fff (white) as an example.
If you don’t want the image to show up in the background at all, then you would need to go into your theme files and remove them from the customize.php and output.php file. That involves editing the PHP code…..but if you would rather just use CSS to prevent it from showing, then that would be much easier.
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