I am sure you did but just in case have you tried different cables and or pcbs. I had the same problem with my Naomi setup I could adjust the colors on the monitor but it was not displaying red at all. In desperation I pulled the jamma cables out of the capcom I/O and cleaned the contacts and after I reseated it all the colors were fine. Anyways just a thought, good luck
You almost always have to adjust the colors when putting in a new board. There’s almost always a little board with potentiometers on it you can use to adjust color, balance, vhold, all that crap
The monitor might just need to be degaussed(?). Is that what it’s called? I’ve been out of the “scene” for a bit, I can’t remember, but there’s that thing what makes the magic happen. But, you know, 100 bucks is pretty good. Fair play!