How do I change the color of the full page background when viewing a lightbox/feedback form?

I am not wanting to change the form background, but the 0.8 opacity of the black background on the whole page.

I'm not sure if I understand your query correctly. You can change the background of the form from the Form Designer and change the opacity by using the slider from the color settings.

Could you provide us with more information that you are looking to achieve? Did you embed the form on any of your web pages? If so, please provide us with the URL where the form is embedded so that we can take a look and provide you with necessary assistance.

We will wait for your response. Thank you!

Specifically, I am NOT looking to change the background color of the form.
When viewing in lightbox/feedback form, the overlay that is standard opaque
-- That is the color I want to customize; NOT the form background; the
color of the overlay that covers the entire screen.

...

Ok. I understand that you want to change the opacity of the outer area of the form. Unfortunately, there is no setting available within the embed code of the form. I have tried few things, but they didn't work for me. If I found any information in this regard, I'll let you know here later.

Thank you!