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