One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,5,7)(3,4,8,6)(9,10,13,16)(11,17,19,14)(12,15,20,22)(18,23,24,21)(26,31)(28,39)(29,41)(32,36)(37,47)(38,48)(46,53)(54,56)(1,3,5,8)(2,6,7,4)(9,11,13,19)(10,14,16,17)(12,18,20,24)(15,21,22,23)(26,31)(27,35)(28,39)(34,43)(38,48)(40,52)(44,49)(54,56)(1,3)(2,4)(5,8)(6,7)(9,11)(10,14)(12,18)(13,19)(15,21)(16,17)(20,24)(22,23)(25,26)(27,36)(28,33)(29,34)(30,31)(32,35)(37,49)(38,50)(39,42)(40,46)(41,43)(44,47)(45,48)(51,56)(52,53)(54,55) involution — undirected(1,4)(2,3)(5,6)(7,8)(9,11)(10,14)(12,18)(13,19)(15,21)(16,17)(20,24)(22,23)(25,27,30,35)(26,32,31,36)(28,37,39,47)(29,38,41,48)(33,44,42,49)(34,45,43,50)(40,51,52,55)(46,54,53,56)(9,10)(11,14)(12,15)(13,16)(17,19)(18,21)(20,22)(23,24)(25,28,30,39)(26,33,31,42)(27,37,35,47)(29,40,41,52)(32,44,36,49)(34,46,43,53)(38,51,48,55)(45,54,50,56)(9,12,13,20)(10,15,16,22)(11,18,19,24)(14,21,17,23)(25,29,30,41)(26,34,31,43)(27,38,35,48)(28,40,39,52)(32,45,36,50)(33,46,42,53)(37,51,47,55)(44,54,49,56)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.