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