My exported ePub pages have a faint yellow background

Operating System Windows 10 20H2

Papyrus Author Version 10.7 Premium

Hi, I’m a new user. I have searched the forums and docs but didn’t find an answer.
I exported a project to ePub (for kindle publishing). The pages have a faint yellow background. I see it in my ePub reader, the Kindle KDP previewer, and a reader mentioned it as well.

Any idea what happened and how to get rid of it? This also shows a faint yellow background on the ePub export page form within Papyrus. I really need the pages to be white. I ind of need to get this fixed and republish my book right away.

Thanks for any help.

Ah, it’s part of the CSS format chosen! The Carter CSS has a yellow background.