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