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