Color change sub categories…

Hi, I would like to be able to change the color of the box around my subcategories on the tabs for the pages… I don’t have any sub categories on there yet, but plan on it when I can get the color changed… Maybe as in a coding I can use for the css… I have already made a few changes there, so I think that is all I need…

My website is https://www.heartcenter333.com

Thanks…