If you would like to change the background for FooBox from transparent to opaque, you would need to add some custom CSS. You can add this into the “Custom CSS” field under the “JS & CSS” tab in your FooBox settings.

In the CSS field, you would need to add the below line:

div.fbx-modal {
	background-color: YOUR_COLOR;
}

Then you can simply replace the YOUR_COLOR part with a CSS color of your choice. For example:

div.fbx-modal {
	background-color: #222222;
}