Page Length Issue in WordPress

On the Main Index template of a WordPress blog, the white “page” which sits behind the content and on top of the body background, shows from header to footer, no problem.

But on the Page and Single Post templates, the footer is not as long as the sidebars because there is less content and the page stops at the footer, leaving longer sidebars with no white page behind them.

I’m using this theme, which I’ve changed to have a white page behind the content and changed the background to a different pattern: Tigopedia Reloaded 2.0 (https://www.sizlopedia.com/tigopedia/)

I’ve done everything I can think of and it’s just not working.

Can anyone help?

Thanks in advance!