In tag-based models for cooperation individuals recognize each other via arbitrary signals, so-called tags. Cooperators use a tag until they are discovered by defectors, who then destroy cooperation based on this tag by exploiting cooperators. If many tags are available, then cooperators can always establish new signals of recognition. This leads to a constant chase: Cooperators establish new signals for cooperation, while defectors constantly try to find out about these signals. Tag based cooperation is intimately related to the green beard effect. While conventional wisdom leads to the breakdown of cooperation based on such green beards, it can be shown that green beards can lead to cooperation if they are worn by red queens.