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