how do I change the ribbon color in my outlook email

Hi, @Amy Thomas

There is no separate setting to change only the ribbon to a specific custom color. In New Outlook, you can change the overall theme, which also changes the color or appearance of the top ribbon.

Click the Settings gear in the upper-right corner, then go to General > Appearance. Choose one of the available themes, or select Light, Dark, or Use system settings.

https://support.microsoft.com/en-us/outlook/change-the-look-of-your-mailbox-in-outlook-com-and-outlook-on-the-web