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