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