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