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