How to change body area opacity?

I’d like to change text area and sidebar area opacity on default template, so that background image will be slightly visible through background. Now whole body area is white and it makes it pretty dull in my application.

Any plans to add option to adjust background opacity, or is it doable only through custom CSS?

What is needed to be added into custom CSS to make that happen?

You can add this in a custom CSS plugin or child theme:

.page-wrap .content-wrapper {
  background-color: rgba(255, 255, 255, 0.6);
.page-wrap #secondary {
  background-color: transparent;

Thanks. it works perfectly.