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