We took one of the six out for the first slot, so there's only five possibilities here. By the same logic, when we go to the third slot, we've used up two of the colors already. There will only be four possible colors left. Then for the last slot, we would have used up three of the colors, so there's only three possibilities left. If we think about all of the possibilities, all of the permutations, and permutations are when you think about all of the possibilities, and you do care about order, where you say that this is different than this. This is a different permutation than this. All of the different permutations here, when you pick four colors out of a possible of six colors, it's going to be six possibilities for the first one, times five for the second bucket, times four for the third bucket of third position, times three.