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