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)(11,14)(12,16)(13,17)(15,18)(19,22)(20,23)(21,24)(25,26,29,33,28,30,36,31)(27,32,35,39,34,37,40,38)(2,5)(3,7)(9,11,13,18)(10,14,17,15)(12,20,21,19)(16,23,24,22)(26,30)(31,33)(32,37)(38,39)(9,11)(10,15)(12,19)(13,18)(14,17)(16,23)(20,21)(22,24)(26,31)(29,36)(30,33)(32,38)(35,40)(37,39) involution — undirected(1,3,4,7)(2,6,5,8)(11,18)(14,15)(19,20)(22,23)(25,27,28,34)(26,32,30,37)(29,35,36,40)(31,38,33,39)(2,5)(6,8)(9,12,13,21)(10,16,17,24)(11,19,18,20)(14,22,15,23)(26,30)(27,34)(31,33)(35,40)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.