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