[deleted] Thanks for this. I decided to add a background to my forum and I was stuck because of the fact that changing the body background does not change the mobile background.
I had to expand the elements which need the transparent rule (middle part of above rules). First, I added #drawer .container
because your background will bleed through the slide out menu on mobile without this. And then also since I use the Pages extension, and since pages have a different name for their hero, I added that as well. This part of the rules ends up being:
header.Hero.WelcomeHero .container,
header.Hero.DiscussionHero .container,
header.Hero.PageHero .container, #drawer .container{
background: transparent;
}