[Feature]: Add colorblind-friendly diff colors setting

[TimCrooker]

Before submitting

• I searched existing issues and did not find a duplicate.
• I am describing a concrete problem or use case, not just a vague idea.

Area

apps/web

Problem or use case

I'm red-green colorblind, and the diff panel is basically unusable for me. The red/green coloring for additions and deletions blends together, so I can't tell what was added vs. removed without reading each line carefully.

Proposed solution

Add a "Colorblind-friendly diff colors" toggle in Settings > General that swaps the diff panel palette from red/green to blue/orange.

Blue and orange are distinguishable across all common forms of color vision deficiency, including deuteranopia, protanopia, and tritanopia.

Why this matters

About 8% of males have some form of red-green color blindness. Anyone in that group currently can't use the diff panel effectively.

A simple opt-in toggle fixes it with no impact on anyone else.

Smallest useful scope

A single boolean client setting that swaps the CSS color variables on the diff panel.

Four files, roughly 60 lines.

Alternatives considered

Custom themes (#1279) would technically solve this too, but that's a much bigger scope.

A focused toggle is simpler, ships faster, and directly targets the accessibility problem.

Risks or tradeoffs

None significant.

It's opt-in, default-off, client-side only, and uses hardcoded OKLCH values that don't depend on any theme variables.

Examples or references

None significant.

It's opt-in, default-off, client-side only, and uses hardcoded OKLCH values that don't depend on any theme variables.

Contribution

• I would be open to helping implement this.

[TimCrooker]

PR up: #1545

[harvitronix]

Looks like the PRs that address this have all been closed.

To reiterate what @TimCrooker reported: the Diff view is unusable for those with red-green colorblindness. This type of colorblindness impacts about 4% of the population, so it's not insignificant.

Amazing product otherwise, thanks for all the hard work.

[juliusmarminge]

Closed as resolved by #10671 (blue/orange diff color palette in appearance settings).