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