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