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