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)(19,23)(20,21)(22,24)(25,26)(27,30)(28,32)(29,33)(31,34)(35,38)(36,37)(39,40) involution — undirected(1,2,5,6)(3,7,4,8)(25,27)(26,30)(28,35)(29,34)(31,33)(32,38)(36,39)(37,40)(1,3,5,4)(2,7,6,8)(10,15)(13,23)(16,21)(17,24)(27,34)(30,31)(35,40)(38,39)(9,11)(10,16)(12,18)(13,17)(14,20)(15,21)(19,22)(23,24)(25,26)(27,30)(28,36)(29,33)(31,34)(32,37)(35,39)(38,40) involution — undirected(1,4,5,3)(2,8,6,7)(9,12)(10,17)(11,19)(13,21)(14,22)(15,24)(16,23)(18,20)(25,27)(26,31)(28,35)(29,34)(30,33)(32,39)(36,38)(37,40)(9,13,14,23)(10,18,15,19)(11,17,20,24)(12,21,22,16)(25,28)(26,32)(27,35)(29,37)(30,38)(31,39)(33,36)(34,40)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.