Dear Karin Johansson,
Good day! Thank you for posting to the Microsoft Community. We are glad to assist you.
Based on your post regarding with "Conditional formatting of Calender in new Outlook". please follow these steps:
Create a new conditional formatting rule
- Navigate to Settings > Mail > Conditional Formatting.
- Select + Create new conditional formatting rule.
- Name your new rule.
- Choose your condition(s).
- Select the font color for the message list to display. Under Preview, you can an example of how the text will appear.
- When you're satisfied with your selection, click OK.

- Click Save.
For detailed information on this feature please see Use Conditional formatting rules to change incoming messages in Outlook - Microsoft Support.
However, if this feature is not yet available on your side, please wait a little since this feature is not yet fully rolled out,
To check for the Status of the features see Microsoft 365 Roadmap | Microsoft 365

Thank you for your time and understanding. For other questions, feel free to add your post to the Microsoft Community team.
Stay safe and healthy. Have a good day!
Sincerely,
Microsoft Community Moderator