If you mean you are going to choose two stars with replacement, what is the probability that the first is B and the second G that is simply the product of the probability of choosing a B and that of choosing a G, so that will be (8/15)(1/15).

If you mean what is the conditional probability that the second is G given that the first is B, then that is the same as drawing a G without any condition so that is 1/15.

RonL