Glad to hear this issue has been resolved!
Thanks for the sharing.
However, due to a recent update in forum policy, the question author now is not able to accept their own answers. So, I have written a brief summary of the solution this issue. Please feel free to accept it as the answer, which would benefit others who also has similar issues in forum.
Summary: [How can I import categories into Outlook 365 from Outlook 10 when user only used Outlook for calendars (not email)]
Issue: How can I import categories into Outlook 365 from Outlook 10 when user only used Outlook for calendars (not email).
Solution: In the meantime, I found a 3rd party application that lets users share calendar categories on a network. I shared the user's calendar categories on her old computer with her new computer and the categories and colors transferred with no problems. The link to the free app is https://www.codetwo.com/freeware/catman/. It was a very easy process.
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