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