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