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