I think there's an anchoring effect in play here. If you select blue -> blue -> green -> blue -> green -> blue -> green…, you land at the population median.
(The point being that, once you get to a somewhat ambiguous point (after two blue selections), you can say "oh, well, compared to the last one this is {opposite color}!", and it seems most people do that.)
(The point being that, once you get to a somewhat ambiguous point (after two blue selections), you can say "oh, well, compared to the last one this is {opposite color}!", and it seems most people do that.)