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