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