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