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