Hi,
As written, the issue is specifically on tabs in single product pages (incl. description), which are white:
https://snipboard.io/F6vR7A.jpg

The background of Single product page is defined, but it’s not impacting tabs:
https://snipboard.io/U9N1RG.jpg

Elsewhere, I did not find anything related to product tabs.
=> what defines the color background of product TABS?

Kind regards