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