The plugin does not have a setting for background opacity so you would need to clear the background color option and use this code.
You need to use a CSS snippet instead of using the built in color setting. You can use the color picker tool here to create a color. Then copy and paste the RGBA value into the snippet samples below. When using the rgba color of your choice: #cff{ background: rgba(0,0,0,0.5); } the alpha channel (last number) is the transparency setting. Values for transparency can be from 0 = 100% transparent to 1 = 100% opaque. A 0.05 would give you a 50% transparent background.
First remove any background color setting you have currently on the feed otherwise the plugin color setting would override your customization. You can do this by clicking “clear” for that setting located at: WordPress Dashboard – Facebook Feed – Customize – General (tabbed page) – clear the Feed Background Color and save changes. Then apply and of the following:
Entire background of the feed:.cff-wrapper{ background: rgba(54, 25, 25, 0.5); }
Background of each individual text post:.cff-post-text{ background: rgba(54, 25, 25, 0.5); }
Background of the date in a post feed:.cff-date{ background: rgba(54, 25, 25, 0.5);}
Background of the link “View on Facebook” in a post feed:.cff-viewpost-facebook{ background: rgba(54, 25, 25, 0.5); }
