how do i change the color theme for the new outlook

could themes be blocked by administrator? we only have organized and dark theme options.

What about the new Modern Themes, it mentions you can customize the background but no option that I see to do that

Hello Jill C2,

Good day to you and hope you are doing well. Based on your further update, we have checked and yes, admin can control (enable/disable) Themes from Exchange admin center. To learn more, please check Create a mailbox policy in Exchange Online for Outlook on the web and the new Outlook for Windows | Microsoft Learn

So regarding your query, you need to contact your global admin to enable Themes for Outlook on the web and the new Outlook for Windows.

If the above shared Information helps you to find required information for your query, you can give vote on it. It help other community members who are looking for this information. At this point your kind cooperation will be highly appreciated.

Thank you so much for your precious time. Stay safe and healthy.

Sincerely,

Ankita Vaidya

there is no theme

The "background" in the classic version of Outlook would be the small area with stripes and circles (some other designs may also be available) that you can see on the File > Info tab.

To choose a "background," use File > Options > General and find the "Office Background" option: