Page Background vs Index Background

I’ve set my site so the front page is static page and the blog index is on a separate page.

Using a child theme, I’ve set the page body background to black. However, now that I have a post, the the posts page is still displaying white (before, it said there were no posts and the body background was black).

After looking through the stylesheet, I’m still not sure what I’m missing.

Any advice would be greatly appreciated.

https://www.ampperformance.us/blog/