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