How to set the current day color in FullCalendar?

I would like to change the color of the current day but only when the calendar is in the day agenda view. My users say they're having a hard time seeing the lines or something. I looked through the documentation as well as the css/js and didn't find a quick way of doing it. Is this even possible without major code changes?

I honestly don't really know what you're talking about, but the jQuery UI fullcalendar widget uses the CSS class .fc-today to style the current day. If your changes aren't visible, try to use !important — it might be that one of the many other classes overrides your styles elsewhere.