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