Assume that a bag initially contains 6 balls: 2 red, 2 green and
2 blue balls. At each step, you choose a ball from the bag at
random, note its color, but do not put it back into the bag.
Instead, you add to the bag two balls, which are of of two
different colors, and different in color from the color of the
removed ball. (For example, if you choose a red ball in the first
step, then after...