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