I think it would be helpful if there was an option to highlight specific categories within a board by changing the background color of the category (see below).
For my personal task board, I have categories for rush requests and clarifications. I'd find it helpful if these categories popped out at me. I currently put tags on each task but this looks a little busy. It also feels redundant to me when I put a tag called "Clarification" on a task I've put in the "Clarification" category.
For team boards, it could be helpful to color coordinate categories by department/project. And/or any new categories could be assigned a color so they pop out to the team members.
Here's a quick mock-up of what I'm picturing:
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