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