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