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