Balls of Yarn are like costumes for minipets. By wrapping this yarn around a certain minipet you can change its colour. Magic! Most of them can be obtained through completing Farm Quests. For a list of what balls of yarn each minipet can wear, go to the Minipet Colours page (on the yarn building in Minipet Island), and click on the minipet you want to check for colours. At the bottom there is also a gallery full of balls of yarn; clicking on each will give you a list of minipets that can wear them.