Selected email background color in outlook on Mac

Hi @Hassen Khemiri 
Thanks for reaching out to the Microsoft Q&A forum.   
I'd love to assist you better with your inquiry about changing the background color when selecting email tiles in Outlook for Mac. To ensure I understand your request correctly, may I clarify the following: 

1.Are you referring to changing the highlight color when selecting an email subject, similar to the example below? 

If so, please note that Outlook for Mac (Legacy version) does not support customizing this setting directly within the app. However, you can change the system-wide highlight color by following these steps:  

Open System Settings > Type "Accent Color" in the search bar > Change the Highlight Color 

This will update the highlight color across your Mac, including in Outlook. Please keep in mind that this change will apply system-wide, so other apps and actions that use highlight color will also reflect the new setting. 

2.Or are you asking whether it's possible to have each selected email display a different background color? 

If that's the case, Outlook for Mac currently does not support changing the background color of individual emails upon selection. 

However, if your goal is to visually differentiate or organize emails, I’d recommend using the Categories feature. This allows you to assign a color-coded label to each email, which appears as a small colored bar in the top-right corner of the message. It’s a helpful way to keep your inbox organized. 

If I’ve misunderstood any part of your request or if you have further details to share, please feel free to reply. I’m here to help and look forward to assisting you further. 

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