One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,4,6)(3,5,7,8)(9,10,15,13)(11,19,20,16)(12,18,14,17)(21,23,22,24)(26,31)(27,35)(29,42)(33,38)(36,39)(40,54)(46,51)(55,56)(3,7)(5,8)(10,13)(11,20)(17,18)(21,22)(26,31)(32,44)(33,38)(34,43)(45,47)(46,51)(48,52)(55,56) involution — undirected(1,2)(3,5)(4,6)(7,8)(9,11,15,20)(10,16,13,19)(12,21,14,22)(17,23,18,24)(25,26)(27,32)(28,38)(29,43)(30,31)(33,41)(34,42)(35,44)(36,47)(37,51)(39,45)(40,48)(46,49)(50,55)(52,54)(53,56)(9,12,15,14)(10,17,13,18)(11,21,20,22)(16,23,19,24)(25,27,30,35)(26,32,31,44)(28,39,41,36)(29,37,42,49)(33,47,38,45)(34,46,43,51)(40,53,54,50)(48,56,52,55)(1,3)(2,5)(4,7)(6,8)(9,13,15,10)(11,19,20,16)(12,18,14,17)(21,24,22,23)(25,28,30,41)(26,33,31,38)(27,36,35,39)(29,40,42,54)(32,45,44,47)(34,48,43,52)(37,50,49,53)(46,55,51,56)(1,2)(3,5)(4,6)(7,8)(9,14,15,12)(10,18,13,17)(11,22,20,21)(16,24,19,23)(25,29)(26,34)(27,37)(28,40)(30,42)(31,43)(32,46)(33,48)(35,49)(36,50)(38,52)(39,53)(41,54)(44,51)(45,55)(47,56)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.