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