It’s basically the link color (which reflects the category color) wherever the link shows. For those using the default stye it would show the small bar, for those using the box style it would show the link text as the category’s colour.
Here’s what it shows now:
Here’s what it would have shown for those using the default bar:
For everyone using the box style it would shown the category name/link in the colour of the category (this is what I’d like to see back):
