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