Update Drupal 10.3.10 -> 10.4.2 change main menu background color

Problem/Motivation

update Drupal 10.3.10 -> 10.4.2 change main menu background color

Steps to reproduce

- update to drupal 10.4.2 (from 10.3.10) with composer; main menu background is now "blue" (screenshot)
- downgrade to drupal 10.3.10 (from 10.4.2) with composer; main menu background is original again (screenshot)

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes