{{contrast_text_color}} helper returns incorrect text color

[fueko]

Issue Summary

The {{contrast_text_color}} helper returns incorrect text color for many
backgrounds due to a typo in textColorForBackgroundColor from @tryghost/color-utils.

Root cause

In @tryghost/color-utils the YIQ formula uses .b() instead of .blue():

Fix

PR submitted to TryGhost/SDK: TryGhost/SDK#905

Steps to Reproduce

Use light color with the {{contrast_text_color}} helper — the returned contrast color will be white instead of black.

For example: #dacafe, #ffa5b1, #a3e6ff

Ghost Version

6.37.1

Node.js Version

v22.13.1

How did you install Ghost?

localhost

Database type

SQLite3

Browser & OS version

No response

Relevant log / error output

Code of Conduct

• I agree to be friendly and polite to people in this repository

[hiSandog]

The root cause points to a very small color-utils fix, but this probably deserves a regression test with the sample colors listed here. It would be useful to assert {{contrast_text_color}} returns black for light pastel backgrounds like #dacafe, #ffa5b1, and #a3e6ff, then keep one dark-background case to avoid flipping the helper too far the other way. That gives the SDK fix a clear Ghost-facing acceptance check.