On private categories, there’s a padlock icon in front of the category title.
I use “box” for the category style setting.
Whatever the category background color is, the padlock uses var(--primary-medium) for its own color, which is grey in my case.
This color is used in the search result preview for the padlock:
I didn’t see this issue on other pages. For example, padlocks are white on the full search result page:
My suggestion is that in the search result previews, the icons in front of a category title when using a boxed style should be the same color as the text (for example, white on a dark background).