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