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