{{contrast_text_color}} helper returns incorrect text color

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: https://github.com/TryGhost/SDK/pull/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

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