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