How to change Navigation title color from grey to black?

Dear authors,

Thanks for your contribution.
I was using this template for our workshop. I noticed some of the titles in the navigation become grey, how can I change them back to black?

Best,
Ray

No file, test, or entry point is named in the issue. Start by locating the navigation-title styling in the repository and reproducing the grey text on the site; done means the affected navigation titles display black.

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