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