edit the background color of my react website

Its a very small and quick job, unfortunately its taking me a few hours to figure it out already and i lost enough time. Its a simple change of background color of a react website in the control panel and on the public facing site. The background or theme color is green and i want to change it to white or dark gray. thats it. below is the image of the website for review. http://144.126.216.249/publish/magazine/ListingPresentation

I have access to the control panel from my local only, you would have to connect with anydesk or some other remote pc type of software. any questions just chat me.