Alternate body class for About page

So the blog I’m working on has 2 tabs at the top “Blog” and “About”

I want the blog tab to be active on every page but the About page. I’ve read – https://elliotjaystocks.com/blog/archive/2008/wordpress-tutorialhow-to-apply-a-dynamic-body-class-or-id/ and https://www.darrenhoyt.com/2007/12/23/use-body-idclass-to-control-wordpress-page-elements/

But I’m not sure how I’d apply these to my exact situation. Could anyone help out. I should also note that I’m functionally retarded at PHP.

Thanks!