More info:
So I went to AMD driver support and found the oldest drivers they still offer, 21.2.1 (Feb 1, 2020)
I did a clean install and the color flashing issue was gone, my second monitor worked as expected.
SO! Sometime between Feb 2020 and now, a huge bug was introduced.
It didn't bother me too bad in the past, since I was able to revert, but now I cannot play BF2042 unless I update.
I'm stuck choosing between a new game, or keeping my second monitor.