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