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