In this way, if you turn out blue or green for the first time, you will fail, so the probability of not being eliminated for the first time is 1/2.
The second time, according to the results of the first time, all the colors except blue or green will be eliminated, so the probability of not being eliminated is 1/4.
These two events are independent of each other, so the multiplication rule is used.
The winning percentage is 1/8.