Change #1050485 had a related patch set uploaded (by VolkerE; author: Dtorsani):

[design/codex@main] tokens: Update diff background and border tokens in dark mode

https://gerrit.wikimedia.org/r/1050485

I would recommend we keep this open as a known issue until we can further refine the colors as outlined by @DTorsani-WMF in T361717#9939699.

Using the 800-level option tokens from Codex, as proposed in https://gerrit.wikimedia.org/r/1050485, would decrease overall usability of the diffs interface for the sake of achieving a specific contrast ratio. The content added and removed colors would be almost indistinguishable from the page background (see below screenshots).

If we do need an immediate solution, I think we should explore applying different decision tokens to the highlighted diff text (color-emphasized rather than color-base) instead of changing any of the background colors. We would just need to be conscious of the fact that the background colors may change again in T333681, possibly requiring this decision to be revisited.

The resulting contrast would be accessible at 4.56:1

I also noticed that in the "default" (side-by-side) wikitext diffs, the diff text already has an increased font weight (bold/700), while the inline version does not...

Maybe this is additional justification for using color-emphasized for both diff styles, at least temporarily?

Change #1050485 abandoned by Dtorsani:

[design/codex@main] tokens: Update diff background and border tokens in dark mode

Reason:

As discussed among Web and DST, we will not change these tokens at this time but will address this as a part of T333681.

https://gerrit.wikimedia.org/r/1050485