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Based on your description, the issue you are experiencing in Outlook for Android not showing calendar color categories for Exchange 2019 accounts is a known limitation. Currently, the Outlook app for Android does not support setting or showing calendar color categories for Exchange 2019 accounts.
There are a few things you can try:
- Sometimes, simply restarting the Outlook app on your Android device can help sync the categories correctly1.
- Make sure you have the latest version of the Outlook app installed, as updates may include fixes for this type of issue.
- Because categories are visible in Outlook for Windows and OWA, you may need to rely on those platforms to manage and view calendar categories.
Please feel free to contact me for any updates. And if this helps, don't forget to mark it as an answer.
Best,
Jake Zhang