I often mix up whether a PR is a draft and final as I do not always pay attention to the subtle difference in the icons.

The latest incident motivating this feature request is the following PR comment.

For our team the PR is treated completely differently if it is a draft. Reviewing a draft as a final PR is annoying for the author and a waste of time and miss of target for the reviewer.

My proposal is to draw the entire background on draft PRs in another color, or to add some other visual clue that is similarly impossible to not see.

I expect to see this change on #3841 and all sub-pages like https://github.com/sindresorhus/refined-github/pull/3841/files if #3841 is a draft.