Color weekend at Fullcalendar

Did you add style to the class in your css file?

You might also try this:

.fc-fri { color:blue; }
.fc-sat { color:red;  }

(or .fc-sun for Sunday) You can see the example here: http://jsfiddle.net/rajesh13yadav/nf9whojL/1/

This worked for me:

.fc-sun { 
color:#337ab7;  
border-color: black;  
background-color: #ffa58c; }

In version 4 you can add an event for all Sundays or another days together using "daysOfWeek".

    events: [
    {
      daysOfWeek: [0,6], //Sundays and saturdays
      rendering:"background",
      color: "#ff9f89",
      overLap: false,
      allDay: true
    }]

I recommend that you use this method because you can easily change it with server-side scripting languages (like PHP, Node.js, JavaScript, etc.)