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