Highlights Views only black & White

I used to be able to hit Highlight (shift+H) to see just my selection. Now it shows the selection but only in a black or white mask. I've tried all three views, Highlight, Highlights BW, and difference. Nothing works.

[Dmitry Kitsov BMD]

Hello, Matt,
most likely you have enabled the Resolve▸Preferences▸User▸Color▸General Settings▸ [v]Mattes Display High Contrast Black and White.
Once you uncheck that option you should see the behavior you are expecting.