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