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