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