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