How to edit Content Background image for Single Post page?

So far no one has been able to help me with this. Some have come close, but have not targeted the issue. Partly my fault since I do not know how to describe issue. Here goes:

How do I change the Content Background for my Single Blog page only? I want the rest of the site to remain as is, but the Single Post page I would like to change its content area by either removing, or changing its immediate background. Right now it is hard to read my blog posts because of the Content backdrop. How do I edit the Content Background in Single Post view?

Others were successful in changing all the areas around the posts, but not the background of the posts itself. Here is an example

example: https://alightthroughthedarkness.com/purge-out-the-leaven-from-among-you/

Notice how hard it is to read my post due to the background. How do I change this background?

Hope I made sense

Thank You

P.S. I have already created and activated a child theme.