XP

Through simple reasoning that if the blue balls were numbered 1 through 3 and the likelihood that you've picked any one of them is the same, the answer becomes obvious. If we assume balls 1 and 2 are in the same box and ball 3 isn't. The likelyhood that you've picked either 1 or 2 is double that of 3 (2/3). The odds are in your favor and you take out the second ball revealing that it is indeed blue.

The wall in front of you suddenly disintegrates and reveals a room with three doors. A blue one, a red one, and a purple one. Assuming that the previous rules apply with blue being good and red being undesirable, why is there suddenly a third option?