On August 1st 1991, Bayer 04 Leverkusen entered the pitch in a friendly versus Liverpool FC in a garish, blue / white / ...green shirt as a tribute to the origin of 'Die Werkself', the Bayer AG. Bayer AG is a German multinational pharmaceutical and life sciences company and one of the largest pharmaceutical companies in the world. The company actually founded the club back in 1904 as a factory team, hence the nickname 'Die Werkself'.