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