Custom CSS for Event Categories in a Calendar

Site URL: https://www.cityyouthmatrix.com/calendar

Hello! I am trying to use Custom CSS to change the background color of events in a calendar block based on the Category that I assign them. I have been unsuccessful so far and am wondering if anyone has any suggestions?

For example, I have three categories for events (General Events, Volunteer Events, and Drop-In Programs). I would like each category to have its own background color in the calendar so that users can easily tell which event corresponds to which category. For example, General Events: red. Volunteer Events: yellow. Drop-In Events: black.