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