Hello,
I am sorry to say that but there is no option in the Theme for now for setting the custom background color for custom pages, you have to use custom CSS with the specific selector/class/id and add/insert the particular custom CSS by editing the particular page into WP Bakery >> Custom CSS option as shown in this screenshot: https://screenshot.net/250g4s7, Hope it will work for you, I have tested the same code on your site and it is working on your site as shown in this screenshot: https://screenshot.net/0ljzxhg Hope this helps :).
Here is the Custom CSS you can use on your site, It will work for you:
.page .main-page-wrapper {
background-color: orange;
}
Best Regards.
.
