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