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