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