I remember learning ~20 years ago to always set `background-color: #fff` since, in those days of Netscape, a user could easily customise their browser's default background color. It was very useful to have someone on the dev team who was weird enough to have done just that! :)
Well, you still can.. (browser.display.background_color in Firefox)
Sure, but that's why I said "easily" - iirc, it was more an end-user feature than a power-user one.