Lightbox embedded form: How can I change the background transparency.

There is one small question. How can I change the transparency of the background around the lightbox. Tell me please.

It's possible to change the opacity of the background, the following code will help you: 

.jt-dimmer {

   opacity: 0.5 !important;

}

This code will need to be added to your website in order to take effect. 

I hope this helps. 

Thanks, it helped !!!