Just now I was using Scrivener 2 and the text color changed from black to purple. Perhaps I used some weird combination of keys. I can’t get it back to black as default. In Preferences, it has black as the default but whenever I try to change the purple to black in the formatting bar it reverts right back to purple. I can’t work like this. Can someone please give me a hint about how to reset the default back to black permanently? (I’ve quit and reopened the app, to no avail.)
Correction: Now it won’t even let me type in anything but purple. Is there a fix for this? Can someone at Scrivener help?
Sounds like you set it to a revision mode. Format>Revision Mode>None. This will get you back to typing in your regular black mode. Then you can also set your cursor in the text and choose Format>Revision Mode>Remove All Revisions to change the text back to black. (This works on a document level, so if you have the purple text in more than one document, load them all into a Scrivenings session, then do Remove All Revisions to set the text to black for all of them at once.)
You are a lifesaver, MimeticMouton. Thanks a million. Fixed the problem perfectly. Thanks again.
Glad it’s back to normal for you! 
You’ll probably be able to identify it if it happens again, but as a clue that it’s not just a regular “whoops, I set the text to a different color” issue, the cursor itself changes color. So if you see the colored cursor, you’re in Revision mode.