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