One vertex per element, one color per generator, with an edge from x to x·s.
(2,5)(6,8)(9,10)(11,16)(12,17)(13,15)(14,24)(18,20)(19,23)(21,22)(25,26,31,28)(27,35,36,32)(29,33,39,38)(30,37,40,34)(1,2,4,5)(3,6,7,8)(9,11,15,19)(10,16,13,23)(12,20,21,14)(17,18,22,24)(25,27,31,36)(26,32,28,35)(29,34,39,37)(30,33,40,38)(10,13)(11,19)(12,21)(18,24)(27,36)(29,39)(32,35)(33,38) involution — undirected(1,3,4,7)(2,6,5,8)(9,12)(10,17)(11,20)(13,22)(14,19)(15,21)(16,18)(23,24)(25,28,31,26)(27,35,36,32)(29,38,39,33)(30,37,40,34)(9,13,15,10)(11,16,19,23)(12,22,21,17)(14,24,20,18)(25,29)(26,33)(27,37)(28,38)(30,32)(31,39)(34,36)(35,40)(9,14,15,20)(10,18,13,24)(11,12,19,21)(16,22,23,17)(25,30,31,40)(26,34,28,37)(27,33,36,38)(29,32,39,35)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.