Add background colors to event categories displayed in the event views of The Events Calendar. This is inspired by the post Coloring Your Category Events.
Settings for The Events Calendar: Category Colors plugin are located in their own tab on The Events Calendar Settings page.
To force a refresh of your CSS, add ?refresh_css to the end of your events URL, or re-save the Settings.
Attribution
Thanks to jonahcoyote for some early help and direction.
Big thanks to Barry Hughes (WebsiteBakery) for refactoring code and Legend Superpowers.