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