grey colour section below primary sidebar

Dear support,
I have a grey section on left sidebar below the primary sidebar in white.
I put

/* white background left sidebar */
.sidebar {
     background-color: #ffffff;
}

to change the colour of the left sidebar but I still have the bottom left section in grey
See in https://compagnielafoliedelange.fr/spectacles/

Where can I change the colour of this part? thanks a lot