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)(25,26,29,34)(27,36,38,31)(28,40,42,33)(30,45,44,35)(32,46,51,43)(37,48,41,52)(39,49,55,53)(47,54,50,56)(1,2)(3,6)(4,5)(7,8)(9,11,14,21)(10,15,18,19)(12,20,13,22)(16,23,17,24)(25,27)(26,31)(28,41)(29,38)(30,39)(32,50)(33,52)(34,36)(35,49)(37,42)(40,48)(43,56)(44,55)(45,53)(46,54)(47,51)(2,5)(6,8)(9,12,14,13)(10,16,18,17)(11,20,21,22)(15,23,19,24)(25,28)(26,32)(27,37)(29,42)(30,46)(31,47)(33,35)(34,51)(36,50)(38,41)(39,56)(40,45)(43,44)(48,49)(52,53)(54,55)(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)(26,33)(27,37)(29,42)(30,43)(31,48)(32,35)(34,40)(36,52)(38,41)(39,54)(44,46)(45,51)(47,49)(50,53)(55,56)(2,5)(6,8)(9,13,14,12)(10,17,18,16)(11,20,21,22)(15,23,19,24)(27,38)(28,42)(31,36)(32,51)(33,40)(39,55)(43,46)(49,53)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.