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