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