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