Amazon sells multi-packs in all kinds of colors for super cheap. http://www.amazon.com/gp/aw/d/B00LM1RO5A for example. It's helpful to have an arsenal. But there's also these http://www.amazon.com/gp/aw/d/B00LNC7X36/ref=pd_aw_sbs_bt_6?refRID=09GZW8BGQBBHP4G4Q03Y