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