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