I think you're right that the subjects in the experiment simply don't think of the 100% blue strategy, and I wonder if there's any way to find out why it's so unaesthetic that it doesn't cross people's minds.

My tentative theory is that conformity is a good strategy for dealing with people if you don't have a definite reason for doing something else, and that the subjects are modeling the universe (or at least the random sequence) as conscious.

Introspecting, I think that choosing 100% blue also feels like choosing to be wrong some of the time, so some loss aversion kicks in, while doing a 70/30 strategy feels like trying to be right every time.

"Even a human" might just be a fair insult.