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