Spoiler for Not exactly a solution, but a thought.
What is discussed is specifying who will say red and who will say blue. However, the prisoners being logical, take from it to say the opposite. A not-so-intelligent PO would give each person the opposite colored hat, and all the prisoners would go free; with an intelligent PO, it would turn into a game of WIFOM, and may free 100 or 0, which doesn't exactly meet the puzzle's criteria. And if the prisoners tried to decide what the PO would do, it may just end up being around 50-50.