SIDE PANEL BACKGROUND COLOR CHAGE

Hello, I need your expertise here.

How to change the Side panel Background color and the width of the side panel.(See screenshot attached to this post)

Basically, I have done my research for 2 hours to look for a solution and I have tested several CSS codes coming from a bunch of websites all over the internet, I have found CSS codes and tested them thru Higend > Highend Options > General Settings > Custom CSS. and none of them work, so I removed everything that I added that didn’t work to avoid any CSS conflict. I also change the color from Appearance > Customize > Colors > Side Navigation/ Navigation bar / Content
None of them changes the color of the Side Panel. Please help me, I know that you guys are expert.

Theme: Highend (minimalist).
Website: https://www.HolisticWellnessNewYork.com
Current Color: Black.(see attached image)
I want to change it into Color:#612482
I need CSS code for this or guide me how to change it please.