🐛 Fixed contrast_text_color returning incorrect text color for some light backgrounds

[eojuma]

Summary

Fixes {{contrast_text_color}} and every other Ghost consumer of textColorForBackgroundColor returning white for light colors such as #dacafe, #ffa5b1, and #a3e6ff.

Root cause

@tryghost/color-utils@0.2.19 used .b() in its YIQ calculation. That accessor is the Lab b-channel, not the RGB blue channel, so many colors were classified incorrectly.

Changes

• Bumps @tryghost/color-utils to the corrected 0.2.20 release from Use .blue() instead of .b() in textColorForBackgroundColor SDK#1031.
• Keeps contrast_text_color delegating to the shared color utility so Core, Admin, Ember Admin, and Koenig use the same implementation.
• Adds regression coverage for the reported light colors.
• Preserves the shared YIQ cutoff with a mid-tone regression case.
• Adds patch changesets for the affected Koenig packages.

Validation

• pnpm install --frozen-lockfile
• Four direct contrast checks against the installed @tryghost/color-utils@0.2.20
• pnpm exec vitest run test/unit/frontend/helpers/contrast-text-color.test.js test/unit/server/services/email-rendering/email-design.test.js — 75 tests passed
• ESLint passed for the changed helper and test
• pnpm nx run @tryghost/admin:build passed, including Ember Admin and Koenig dependencies

Fixes #27797

Checklist

• I have read and followed the Contributor Guide
• I have explained my change
• I have written automated regression coverage
• I have run relevant tests, lint, and builds locally
• I have added the required changeset

[coderabbitai]

Walkthrough

The pull request adds tests for black contrast text on three light backgrounds and white contrast text on a mid-tone background. It updates the workspace catalog to @tryghost/color-utils version 0.2.20. It also adds patch release entries for @tryghost/kg-default-nodes and @tryghost/koenig-lexical.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The dependency update and regression tests address issue #27797 by correcting contrast colors for light backgrounds.
Out of Scope Changes check	✅ Passed	The dependency update, regression tests, and related changeset support the stated contrast color fix.
Title check	✅ Passed	The title clearly summarizes the primary change: correcting contrast text colors for light backgrounds.
Description check	✅ Passed	The description directly explains the contrast color fix, root cause, changes, regression tests, and validation.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[nx-cloud]

🤖 Nx Cloud AI Fix

Ensure the fix-ci command is configured to always run in your CI pipeline to get automatic fixes in future runs. For more information, please see https://nx.dev/ci/features/self-healing-ci

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Command	Status	Duration	Result
nx run ghost:test:ci:integration	✅ Succeeded	2m 18s	View ↗
nx run @tryghost/admin:test:acceptance	✅ Succeeded	7m 15s	View ↗
nx run-many -t test:unit -p ghost,@tryghost/ada...	✅ Succeeded	6m 8s	View ↗
nx run ghost:test:integration	✅ Succeeded	3m 5s	View ↗
nx run ghost-monorepo:lint:boundaries	✅ Succeeded	23s	View ↗
nx run-many -t lint -p ghost-monorepo,ghost,@tr...	✅ Succeeded	3m 47s	View ↗
nx run ghost:test:legacy	✅ Succeeded	3m 2s	View ↗
nx run ghost-admin:test	✅ Succeeded	3m 30s	View ↗
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☁️ Nx Cloud last updated this comment at 2026-08-10 19:21:06 UTC

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.45%. Comparing base (5406605) to head (e76a291).
⚠️ Report is 25 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #29834      +/-   ##
==========================================
+ Coverage   75.40%   75.45%   +0.04%     
==========================================
  Files        1606     1605       -1     
  Lines      140381   140484     +103     
  Branches    17389    17429      +40     
==========================================
+ Hits       105860   106004     +144     
+ Misses      33444    33432      -12     
+ Partials     1077     1048      -29     

Flag	Coverage Δ
admin-tests	55.97% <ø> (ø)
e2e-tests	77.60% <ø> (+0.05%)	⬆️

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