There are 4! ways in which she can hang the bulbs, which means 4x3x2x1. this is 24 ways. g o b p g o p b g b p o g b o p g p o b g p b o o g b p o g p b o p g b o p b g o b p g o b g p b o g p b o p g b p o g b p g o b g o p b g p o p g o b p g b o p b o g p b g o p o b g p o g b
of these ways, there are 12 where green and brown aren't next to each other