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