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