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