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