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