A group of Microsoft Products and technologies used for sharing and managing content, knowledge, and applications.
Dear Zack,
Ther default background color of the web part is white and there is no built-in option changing it.
From the screenshots, it seems that the font color and the background color is changed by the custom CSS code deployed by someone in your organization.
If you aren't the administrator, you may contact him and check whether some CSS code extension package has been deployed on the Apps for SharePoint page in the SharePoint admin center. If yes, that may be the reason of the behavior and you may let him remove the solution package and then refresh the site page to see the result.
Your effort and time are greatly appreciated!
Sincerely
Cliff | Microsoft Community Moderator