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