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