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