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