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