set background to transparent

Hello,
I’m having trouble setting the background of the calendar to transparent, currently I have to choose a color and there is no way to set the transparency. Do you know the css to change this? I’ve tried with
div.owac-calendar-container {
background-color: transparent !important;}

but it still appears white.
I have a pattern behind the calendar so I need it to be transparent…

thanks !
kind regards
Jeanne