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)(11,23)(12,27)(13,19)(14,20)(15,22)(16,21)(17,26)(18,32)(24,29)(25,33)(28,34)(30,38)(31,37)(35,36)(39,40) involution — undirected(9,11,15,26,16,19,14,25)(10,17,20,23,21,33,22,13)(12,28,31,24,32,39,30,36)(18,35,37,40,27,29,38,34)(2,5)(6,8)(9,12,15,31,16,32,14,30)(10,18,22,38,21,27,20,37)(11,24,25,28,19,36,26,39)(13,29,17,34,23,35,33,40)(9,13,15,17,16,23,14,33)(10,19,22,26,21,11,20,25)(12,29,31,34,32,35,30,40)(18,36,38,39,27,24,37,28)(1,3,4,7)(2,6,5,8)(9,14,16,15)(10,20,21,22)(11,25,19,26)(12,30,32,31)(13,17,23,33)(18,37,27,38)(24,28,36,39)(29,34,35,40)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.