‘We invented the name Blaue Reiter whilst sitting around a coffee table in Marc’s garden at Sindelsdorf… we both loved blue, Marc liked horses and I liked riders, so the name came of its own accord.’ Christened so casually by Wassily Kandinsky and Franz Marc in 1911, the Blue Rider was always more of an idea than an art society, but the Tate Modern’s new exhibition – the first in the UK since 1960 – makes it sound more contemporary by describing it as a transnational collective.