I have had a few machines that occasionally have strange color combinations and you can’t see the logon box to view what you are typing. I finally put the right words in the search to come up with the answer:
SYMPTOMS
After you press CTRL+ALT+DELETE to log on to a Microsoft Windows Server 2003-based computer, the logon screen turns black. Although you cannot see what you are typing, you can successfully log on to the Windows Server 2003-based computer. Then, after you successfully log on, the screen becomes visible.
Note This symptom may occur on both the terminal server sessions and the local console. Additionally, this symptom occurs even if you start the computer in Safe mode.