This reminds me of a puzzle in NeMoren's Vault. Next to a sealed door, there's a plaque that reads something like:
orange blue red yellow red green blue yellow orange
You have to do the same thing as in that test. It was too easy in my mind, so I had a monster providing time pressure. Well, the party needed three tries to get it open, and they were nearly dead by that point.
P.S., 100%