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