"If you are reading the comments because you are undecisive, just go for it. You are getting what you are looking for: rainbows. They are easy to put on, and remove (and move around). They have to be in direct sunlight, so if your window is on the north side, and the weather is cloudly, don't expect great result. Get one pack more than what you think you need, because the more you put on your window, the better it looks."
Electrostatic Rainbow Hexagons, Repositionable, Window Decoration Set of 12 Pieces