Greetings I am using fullcalendar v.5.10.1 for my project and I want to change already passed days color to more grayish(see picture)/ I cannot use Ajax only CSS styles. What styles I need to apply to make (marked) colons be more grayed or complete different color?

Already tested and it is not working if adding this styles to calendars CSS overwriting its CSS styles
.fc-past{background-color:red;}
.fc-day-past{background-color:red;}
.fc-past {background-color: purple;}
.fc-day-thu{background-color:red}
btw as option I pass to fullcalendar, validRange parameter https://fullcalendar.io/docs/validRange
Okey I found the solution. To change grayed fields if you are using validRange as option. need to change this styles
.fc .fc-cell-shaded,
.fc .fc-day-disabled {
background: #E5E5E5;
background: #E5E5E5;
}