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