Hi @Fiona Martin ,
Welcome to our forum.
I noticed that you are working with an older version of Outlook client, in order to get a better user experience, it's recommended to update your client to the latest version.
For your issue itself, I understand that sometimes the message text would turn to white automatically when you write it in your Outlook for mac, is it right?
If so, based on my research and test, it would occur when we switch to the format of message to plain text (turn off HTML) accidently and set the font color of plain text to white. In this case, it's suggested to check your font setting in preferences and change it like below:
If the issue still exists or that's not your case, please feel free to post back.
If the response is helpful, please click "Accept Answer" and upvote it.
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