Recently used my Microsoft Authenticator to access an email address on my mobile phone which I only needed temporary access to. After which I removed the email account from Outlook on my phone only to have it remain (greyed out) within Microsoft Authenticator.
To remove the greyed out account from Microsoft Authenticator I had to go to my phones’ “Settings” then “Accounts and backup” followed by “Manage accounts“. To my surprise, even though I deleted the email address from Outlook, the email account was still there. Once I removed the email address and reloaded Microsoft Authenticator the greyed out account was gone.
I hope sharing my experience on how I successfully removed an unwanted, greyed out account from Microsoft Authenticator has helped you.
Let me know if you found any errors within my article or if I may further assist you by answering any additional questions you may have.