I'm so sorry, I'm getting my Ceronix conversations mixed, this is a PE, not a Fortune. You do need to verify the wires from monitor to back board but also trace them on the back board from source to pin out to the board. Or at least look for something that looks problematic (broken traces). Is this a PE or a PE Plus, I thought PE had black cable connectors that plugged directly into the board. This has back-board connectors.
One thought, I haven't looked at a PE board closely but any chance it has a transistor or color pot for each color? I can't see the picture clear enough. If there are 3 transistors next to each other on the board that's a good place to start. Same deal, you don't want any shorts. In your situation one of them would test like a diode (good), two would be different (shorted or open).
EDIT: Looks like you have a PE+ Super Board. Take a look in the NLG File system, there is a manual that has a circuit diagram. I highly suspect there is a color controller section on the board. If you can't find a blatantly obvious problem you might need to send the board into K-Lar.
Chris