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