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