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