Bug: Module headings not visible on some courses

[kathrynwp]

Issue

On Learn.WordPress.org with the current (old) theme, module headings on some courses are white, so they are not visible.

Example: https://learn.wordpress.org/course/beginner-wordpress-user/?new-theme=0

Step-by-step reproduction instructions (optional)

• Visit a course page
• Make sure you're using the old theme (exit the new-theme preview if applicable)
• Look at module headings

Screenshots or screen recording (optional)

Other information (optional)

Tested in Firefox, Chrome & Safari on Mac OS 14.5 (Sonoma).

cc @adamwoodnz :)

[kathrynwp]

Apparently this is not affecting all courses. For example, the Beginner Developer course module headings have a black background, which makes the white headings visible:

[adamwoodnz]

This was caused by a Blueberry border being set on the Course Module, which is a color not available in the old theme. I'm not sure how it was set, but I fixed it by toggling the border setting off and on again