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