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