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