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